What's his name?
First of all, cats don't meow for "no reason".
Cats talk, so if he's not meowing because he's sick, or lonely or neglected, he's just talking. Some cats are more vocal than others.
It's very common for cats to be talky in the middle of the night, but he will probably outgrow most of it. Reacting to it, in any way, only reinforces the behavior.
If he is not neutered, you need to have that done as soon as possible.
Have there been any changes in your household that could be causing stress? New person, one less person, new furniture, new neighbor cat outside?
How long has he been with you?
Get some feliway plug in diffusers, they will help reduce stress.
If this is new behavior, and there isn't anything new happening in your household I recommend a trip to the vet to rule out illness.
Be sure to PLAY with him every day.
All the toys in the world won't make any difference if you don't give him Interactive Play.
Play with him at the same time every evening.
Play vigourous active Games that have him running and jumping, to burn off some energy. (I can give you Game suggestions if needed)
If you play Games with him every night at the same time, he soon will come to expect and look forward to this special Bonding time with you, and it will go a long way toward making him feel secure and settled...and sleeping through the night
This, also, is good for your son as he grows, to learn how to care for and play with cats.
Cats, contrary to popular belief, are social animals, and require interaction and attention with their humans on a daily basis.