Hi Michelle!
It sounds like you are going to have magical time at sea with three generations of your family! My first cruise was also with a group of 15, and we had the most amazing time cruising the high seas with Disney!
On formal night, many girls do dress up like Disney royalty! Some girls bring costumes aboard and others purchase them onboard. The Disney Fantasy also has the first
Bibbidi Bobbidi Boutique at sea where girls ages 3-12 can be magically transformed into their favorite Disney princess by their very own Fairy Godmother-in-training! Appointments are available throughout the day and can be made 75 days prior to sailing online in the Planning Center at
www.disneycruise.com.
When my son was younger he wore "jon jons" on formal nights. Now that he is a little older, I dress him in a coat, tie, and khaki pants. I have also seen some boys in Prince Charming or Peter Pan costumes as well. A button down shirt with pants or a nice polo shirt would also be fine.
I hope my suggestions help, Michelle! Please keep me posted on any other questions you may have during your cruise planning!
Have a magical day!
Nancy