Hi Stephanie!
Thanks for coming back to visit me! Sounds like you guys are REALLY planning a magical vacation! A Disney Cruise is very special, your kids will certainly enjoy the Fantasy. My son LOVES cruising with Mickey Mouse!
Since it's your first time, I suggest you take a whole day for each park and one whole day for exploring outside the parks. The Grand Floridian is a beautiful resort, so you will want to take some time to explore, swim, and check out the resort activities they have to offer. You can split up your park days so you have a relaxing day in between to recharge for more park fun OR take a relaxing resort day at the end of your Walt Disney World vacation before you start your cruising adventure.
Talk to your girls and take a look around the Disney World website together. Have each of them pick out something that they HAVE to do and plan around those things. Maybe it's a ride, a show or a visit with their favorite character. Mine is Snow White, so no visit is complete without a picture with her.
How about a water park? My kids are water babies, so we spend more time at
Typhoon Lagoon and
Blizzard Beach in the summer than at any of the other parks. This is a concrete "must do" for my family. The weather in October should still be lovely for a dip in the water.
If you guys aren't too tired at the end of the day, stay for Wishes at the Magic Kingdom, Illuminations at Epcot, and Fantasmic at Hollywood Studios. No one puts on a pyrotechnic show like Disney and you have to see these with your own eyes.
I hope I've given you a starting point. Come back and see me if you have more questions.
Have a magical day!
Leslie