You can look through any magic catalog or any on-line store listing and see all of the effects that are available for performing children's shows. So that question about tricks is one you can easily answer by yourself. Every magician in the forum has a favorite trick or book and will happily share that information with you. But the title of your thread is "A bit of help, please" and I don't think compiling a list of my favorite tricks or books is going to be any help to you at all.
If you want to find out whether or not performing children's magic is a good career choice for YOU, some questions need to be answered first. Do you like children? Not in ones and twos, but in large groups? Are you comfortable talking with children? Notice I asked "with" and not "to" or "at." Talking WITH children implies that you listen to their responses and that there is a back and forth dialogue going on so the conversation is as much about THEM as it is about YOU.
We haven't even gotten into the subject of doing magic tricks for children and there are lots of questions still to ask, and things you should be asking yourself before you start.
So the BEST way would be for you to find a magic mentor in your area, someone who actually performs magic for children. Watch this person at work, talk to this person and explore with him or her the possibility of transforming yourself from a close-up magician to a children's magician.