Great for them!! Its good that BOTH will be able to do pre-team together. They'll get more strength/flexibility work plus learning and polishing skills. Usually pre-team classes don't take up that much time during a week, so that it interferes with family time and other activities they want to do. Will you have a chance to watch some classes before they start? Might be a good idea, so your dds have a little idea of what to expect and how it is different from what they are doing now.
As someone mentioned it is "limbo" for the move to team. Normally, pre-team programs do no fund raising which means you don't benefit from any of that and you're not considered part of the team booster club. Its a fun time to watch them grow and learn new things. Keep us all updated come 2008!!