Just be aware that with each season the dog is allowed to have, the chance of mammary tumours increases. Vets used to believe that having a LITTER was better for dogs! Then it was having at least one season. This has completely changed and I know few vets who have this opinion any longer (though know some out in the country who still advise on a litter first -- despite the fact that 25,000 dogs are pts in Ireland every year thru pounds alone; a lot more are pts in the greyhound industry, by vets, and through drownings etc. Why vets advocate a practice that means puppies die, I do not understand in this day and age, but some do.
For most people, if they are spaying/neutering, it is a lot easier and more manageable for them to do this before the first season and before the males start spraying etc behaviours. If people choose to wait, just be very, *very* aware that you need to manage your dogs carefully until the point when you neuter as a sexually maturing dog will do very different things, and runs very differents risks, than a younger dog. Many males will take off if given half the chance, they can roam for miles, they can become quite unwelcome visitors to others' houses as, in my experience, they will *always* spray and hence must be watched constantly. Females with every heat run a risk of pyometra, which is often fatal, and gradually increase their chance over a lifetime of mammary tumours, regardless of whether you do eventually spay, and can be very determined to get mated when they come into heat and must be closely guarded from having that chance for around 4 weeks of confinement. Only one second is enough time for a male and female to tie and you cannot separate them easily at that point, if at all (it is physically impossible after a certain point -- and they don't even need to tie for her to be impregnated). They also often spot blood around the house. I am far more worried by people who keep females entire than males as most people with females seem totally unaware of the facts of life with dogs and run high risks as a consequence. Also: intact male and female cavaliers are prime targets of thieves and are often sold on to backyard breeders and far worse -- puppy farms. They are stolen to order in Ireland and the UK and is one of the breeds most often taken, say police. It's one reason all my dogs have tags that clearly state they are chipped and neutered as if they were ever taken, I'd hope the thief would realise they are valueless for breeding.
There are people who are well able to manage these things and balance the greater responsibilities and inconveniences against letting the dog reach sexual maturity and then neutering. But there is little evidence this makes much difference to the health of a dog or its size or appearance. Some people feel it does though only on the smallest scale -- a half inch to an inch of height, perhaps, for example. Jaspar and Leo were neutered at around the same age and while Jaspar is lankier, he was as a puppy. Leo is a cobby compact CKCS. Lily as well is very small and compact yet surely was neutered at around 6 months going on how young she was when I got her from the pound, already spayed.
Coat does sometimes change on neutering but this seems to depend entirely on the dog and its lines as well as whether people allow the dog to become overweight. I have seen many neutered females with unaffected coats. I have seen breeding females neutered at age 6, whose coats go more cottony. But this is a minor cosmetic issue vs. the overall health of a dog and risk of litters. None of my males have had their coats affected by neutering at under one year.
FWIW, MOST of the cavaliers I get into rescue that are found straying or picked up by dog wardens are unneutered males, often found following around female dogs, or females in heat. They DO do their best to take off. The call of nature is very, very strong. I have only had ONE spayed female in rescue -- Lily! -- excepting two that were spayed by the breeder before going to rescue, and NO neutered males excepting a few I was rehoming for the owner.
Just some other perspectives.