Welcome back, Anna!
What a bummer that the
Port Adventures you were hoping to book were already sold out. But, the good news is that guests change their plans all the time, so quite often there will be spots open up on many of the Port Adventures. I highly recommend you check into your My Cruise Activities page a few times each week, just to see! You may see an adventure open up! Once onboard, you can also visit the Port Adventures desk and chat with them about any additional spots that might be open, or get on a waiting list.
I wish I knew which itinerary you were sailing and which of Disney's magical ships you'll be on, because I could better give you ideas about what to do on your own in those ports of call. But, no matter which ports you'll stop in, you're always welcome to get off the ship on your own for some exploring. You may want to do a bit of research into what interests your family in those ports. Check online and see where you might want to go, as you can always grab a taxi at the port to take you there on your own. I highly recommend Disney Cruise Line's Port Adventures over touring on your own, as they guarantee you're back in time for the ship's departure, and the ship always knows where you are. Plus, they get inside access to even more magic on these adventures. But, if you really have your heart set on a particular experience in a port and the Disney adventure is booked, you can go on your own. In addition, most ports have great shopping and cultural activities just outside the port area, so walking around to explore on your own right there is always an easy option too. In some ports, my family and I prefer to stay onboard the ship and take advantage of the less crowded pool deck and AquaDuck or AquaDunk while other guests are out on adventures. That makes for a fun day too!
Good luck, Anna!
Marcy