Paediatric is under 6 months, Early is under full maturity (around 18 months- 24 months+).
Paediatric neutering( PN)/spaying (PS)& Early Spay (ES)/ Early Neutering (EN) is damaging and problematic, there are still a handful of vets who follow outdated information and recommend to new owners. They only recommend it because of ‘overpopulation’ in dogs, the overcrowding in rescue centres , outdated information, the stigma against certain breeds, and behavioural issues such as marking or aggression. 
Medical necessity aside (1 testicle e.g) while there are a handful of benefits for this procedure, through extensive research by grad students, researchers, vets, vet hospitals and those others specialised- the research proves it’s actually not as beneficial as it seems for our beloved animals, that is comes with harsh and even irreversible side affects and consequences. 

As breeders, it should be our duty to guide our clients the best way we can, just as we recommend which food to feed or how to toilet train. Of course, this information is useful to pet owners too! 
In my opinion, as well as many, unless a dog medically needs it they should stay intact. However if you really want the procedure to de-sex done, wait until they are at least 2 years old (This of course isn’t a set rule, it’s a breed-by-breed case, so if you have a larger dog they’d be neutered at a greater age compared to a smaller breed) or looking into other options such as Ovary Sparing Spay (OSS) and vasectomy. 

PN/PS ES/EN prevents several types of cancers (testicular for example) while increasing the risks of 20+ more , bladder cancer for example, osteosarcoma (bone cancer) , cardiac hemangiosarcoma (cancer in the blood vessels, common), splenic hemangiosarcoma (cancer in the spleen, most common spleen cancer) , and the even more common prostate cancer. It doesn’t stop there, it also increases the chances of hip problems such as dysplasia , stunts growth, incontinence, joint issues, Atopic dermatitis, autoimmune hemolytic anemia, hypoadrencortiscism, immune-medicated polyarthristis , inflammatory bowel disease, and the list goes on. 

Your dog/Female NEEDS their hormones and their growth palettes to grow, imagine this being puberty for humans, we need to go through our different stages and receive our hormones. Otherwise, your dog/female development is ‘stuck’ in a puppy like manner and will never mature to their full potential; Some of the Growth palettes don’t close until 17-19 months+ (of course, breed by breed basis). 
For example, your girls NEED their first season, the development stage is evident, their coat is glossy, they fill out appropriately, their structure changes- they MATURE! However when you spay before their first season, they’ll develop what’s known as a ‘spay coat’, which is less glossy, sheds more and can even change the density and quality of their coat ; PS/PN ES/EN affects their growth pallett, which means they may be more grow taller than average, leggy’, more lanky, and ‘roachbacked’. 

Now of course, there are several variables that can affect a dog’s structure and development such as their diet, environmental , and training regimen; we do have ‘throwback genes’ too , just as we can look like our (great+) grandparents , so they can also have slimmer features down to genetics. Each pup to their litter won’t be identical, some are genetically slim while others are genetically slow growers. Or even if the breeding pair wasn’t compatible , producing pups that reflect that- (choosing a sire for a dam takes a lot of factors, however when all things are ticked off (i.e health testing ect), they should also be physically compatible and match) however there is a visual difference between genetics and stunted development from PN/PS EN/ES.
There’s also a common myth that states a girl should be bred from before you spay her- this just isn’t true either.

Another recommendation from vets too is to early neuter/spay or paediatric neuter/spay if your pet has behavioural issues. De-sexing WILL  NOT put a stop to issues such as marking, aggression to you/other people, food aggression, biting, aggressive with other dogs, or the most common - humping. Only a TRAINER or behavioural specialist will help fix these issues as this is a behavioural problem. 
For example, humping isn’t necessarily a sexual desire for dogs, this can simply be pent up energy, overstimulation, or over excitement! This can commonly happen when guests arrive, meeting new people/dogs, playing , or come home from a walk. There’s also recent studies that have shown that PN/PS EN/ES actually increases fearfulness and even aggression in dogs, among other psychological and behavioural issues. 
You need to train your dogs, give them a purpose. Your working breeds absolutely thrive on a purpose but they need to be trained properly, this goes for every breed too. 

Also to add, this isn’t to bash vets! So please, no harsh comments insulting them. They do a brilliant job, however just like humans, when they give a recommendation for a procedure or give a diagnosis- always ask for a second opinion, even a third or go to the relevant specialist. I commend vets for all they do!
Remember that this is always a personal decision, you know what’s best for your lifestyle and your family so this post isn’t to pressure you to keep intact pets, only to provide information that isn’t always easily accessible or wildly spoken about. 

So in conclusion, your decision is your decision, the recommended age to desex is 2 years minimum (breed by breed basis so you may have to wait longer depending)to allow your dog to go through ‘puberty’ , to wait for their growth palettes to mature and close, and for them to fully mature. Or if you want to remain intact you can, there’s other options too, such as vasectomy and Ovary Sparing Spay, this prevents unwanted litters while also allowing them to keep their hormones to mature properly without the increased cancer risks, this procedure can be done at any age as it doesn’t affect the development.

For more in depth advice, consult your local vets to make a decision that fits your household.

I can provide more links if anyone is interested- these are all written by vets, animal hospitals or those qualified. 
Also, it you have any pictures you’d like to contribute, please feelnfree to inbox me. 

https://iaabcjournal.org/spay-and-neuter-surgery-effects-on-dogs/

https://www.vrcc.com/oncology/does-early-castration-increase-the-risk-of-cancer-in-dogs/?fbclid=IwAR17LdiwJLUF__g1LyCh0ZnnjTMYlUql8KmVTYd5UCIX72Y61HTzxD7YBHA

This one is the BEST link 
https://drive.google.com/file/d/1CIlv7XHpc9OnBMb5f_Njbm5aGyVSpmjW/view?fbclid=IwAR2mwXT6K71qADwxHxZpBVHTBfzut_rxF4ZqhXxlPjVf-BRCToLLS7oEbhE

https://www.dogsnaturallymagazine.com/long-term-health-risks-benefits-spay-neuter-dogs/?fbclid=IwAR04bcq1K1JHrMViWlg6rIOK2muSahV7JeQJwr4sH9RE0FTTuJnsjUG8nnk

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4096726/pdf/pone.0102241.pdf?fbclid=IwAR0MSeMFVCUF1elU5yMhNY1x5IaXeL4wl8YINvAYVpZfPMPfq8ns_yu3g4c

https://www.psychologytoday.com/us/blog/canine-corner/201702/are-there-behavior-changes-when-dogs-are-spayed-or-neutered?fbclid=IwAR3WURZDhmWitmkTqeyeiz1FzGQVFVSLc-eiqFL34ODK8sRWMcGOuJ7gINc

http://www.naiaonline.org/pdfs/LongTermHealthEffectsOfSpayNeuterInDogs.pdf?fbclid=IwAR1A9Bk78FM1XWsHSg2KtX-sKWdb3hOdgZmIqSOhnexHt59igf1PcYN3Tf8