Looking for ways for my sons to communicate long distance?

My son & my stepson are very close. They go into almost into their own little world so to speak when they are together. They are 11 & 14 & both have forms of autism. They both get upset when its time for my stepsons visit is over so we are looking into ways they can communicate for the 12 days in between visits. My stepson lives about 70 miles away so walkie-talkies are not an option. We would like to find a way, an inexpensive way, for them to be able to communicate with each other other than just calling each other on the phone. We thought of maybe getting them cell phones so they could text each other back & forth but I don't know how they would handle that. I'm not able to afford full keyboard phones for them & I'm not sure they could handle using the 'old fashioned' way of texting. Any other ideas?