G.B.
I have email addresses for each of my grandchildren. I ALWAYS make their birthyear the same as mine or another adult. Why expose them to the possibility of someone looking at profiles especially for children. Then I have them set up as a sub-account to my primary account. That way I have full access to their accounts.
If they go on Facebook or any other social network I always go to privacy and hide them from public searches. I am on their accounts at least once a day playing their farms/aquariums with them and the only people they are friends with are people I personally know or people that my friends trust to have on their children's accounts. For instance, my friend in another state has neighbors that she is close to that have kids too and I allow my kids to be game neighbors to the friends she has suggested because I trust her judgement with her kids and who she lets friend them.
I find this to be a good way for the kids to keep in "special" contact with their mother and fathers, they get really excited when they get an email from someone they love. I also send e-cards and things to them to make them feel more special too.
As for the cell phone I would go to my cell provider and go by their suggestions so that the cell phone would be compatible with my billing.