No, there are no such restrictions. If you can play Clash of Clans then you can also play Clash of Null. Both are the same game with the same troops, buildings, heroes, etc. Kids can play it too, also, this private server is ad-free, so, no need to worry much. If you wish to install this game in your child's mobile, go ahead, they will enjoy the game with unlimited gems. Instead of spending your real money, they can unlock everything for free using unlimited gems.