Xbox Kids

You are going into Parental Advisory there mate, Most adults supervise their children, If a child is Playing a game rated above their age then chances are their Parents either dont know the game or have cleared the game for play for their child,. either
way it is the parents decision in this.

kid 1 and xbox 1

make sure kid 1 has the gold or ultimate subscription

make sure he sets xbox 2 has home

as long as you have internet kid 1 can sign in on xbox 1 and play normally.

kid 2 and xbox 2

make sure kid 2 signs in on his name on xbox 2 and he should have the same benefits as kid 1 as xbox 2 is kid 1's home console

https://www.thewindowsclub.com/xbox-one-educational-games-kids

here you go, kid friendly and educational games for xbox one

With a great amount of supervision, and utilizing the Family Settings provided to you, the
Family Gold membership would be your best bet.

Sorry for late reply

In that case, log into the adult account that has control over the Family Group.

After that, Select Profile & system > Account > family Once thee, choose your child account Gamer tag Next, go to Privacy & Online Safety -> Xbox Live privacy -> View Details & Customize.

Or you can do that from the website; by signing into the adult account
here. Then Choose your child account Gamer tag . then Select either the
Xbox One/Windows 10 Online Safety tab or the Privacy tab. and update the settings that you want to change.

Hope it helps.