Very few people realize declawing a cat means amputating the end of each toe. Worse, in the process of doing the amputation bits of bone fragments are often left behind and they keep growing causing pain and disability for life. With sore feet you kitten will look for soft places to use the litterbox because its instinct to scratch will be painful otherwise. Soon there will be poop in your rugs and laundry. He will also be more stressed and likely to bite because he cannot defend himself without his claws. Should he get out or be attacked by a larger animal he will neither be able to fight back or climb to safety.
They look like they want to go out to play and have a little adventure. Unfortunately, even for an adult cat the outdoors can be a very dangerous place. Wild animals, dogs, busy roads and other cats... some with illnesses that can kill him. Then there are the people who will "adopt" your cat. Siberians are beautiful cats and very friendly. Even with the best case scenario you invest a huge amount of money in your pet. Why give it away to some random stranger or worse let it be killed. Why put your family through that. Keep them in.
Tiny kittens are so cute. Experience the miracle of birth. You have heard or thought this before. Everyone has. Reality is cats can have problems when in labor and die. Not every kitten survives. Letting your child experience the miracle of birth can also mean forcing to experience the tragedy of death. Even if they do not get pregnant they advertise looking for love. The cat version of Match.com is spraying urine all over the house and "singing" late into the night. For everyone's sake and sanity neutering is a good idea. It also keeps the allergen load low.