Welcome tennispretzel! When our whole family cruises together we are only 8 - but even then coordination can be daunting. We follow the same rules as BettyK. We talked about the plans and if something works out to do together great and if not we meet up for predinner drinks and dinner. After that - each to his (or her) own!
How lucky you are to have so many family members wanting to cruise together for your mom's birthday!
