A word of warning, be careful to make certain that you do have the No roaming / No Long distance charge plan or you will run up quite a phone bill. Many do have it, but I know that my plan has No roaming in the NorthEast, but Florida is roaming, and it's expensive.
Think of the Motorola as CB radios. They are NOT private, and even with 14 channels, 28 sub-channels there is only 392 combinations, so there will be other on your frequency. But we still found them quite useful and we only had 10 channels when we went two years ago. Npte also that the range does not necessarily cover the entire park.
BTW, I had my cell phone with me last time as well, and If I recall correctly I found a number of dead spots in the parks where the phone was useless. This may have changed.