My son will be 10 in April and we would like to buy him a prepaid cell phone so that when he is out playing with neighbors he can check in with us and we can call him. What is the best option? We are w/Tmobile. We have an old phone we could pay $20 for a sim card, no activation fee and spend $100 for 1 year 1000 minutes service. But I don't know if we should look at tracfone, straighttalk, etc. What are your opinions?