L.W.
We went in late October too and had a blast. Our kids ranged from 12 down to a few months at the time. We stayed in one of the Disney hotels and used the meal plan (2 main meals(these are generous. Some restaurants use 2 meals up if you are doing a character restaurant we had no problem having enough to do this we split meals for the adults sometimes, there was soo much food) and a snack(can use as breakfast...but we wanted to get a quick start and brought granola bars and such for the room and hit the parks as early as we could)...it made life easy and we loved the restaurants we chose. You can take the kids back to the room early get the girls down for the night and either switch off with your folks to babysit or hire one of the babysitter from the hotel, and head back to the parks in the evening for some adult time. When we went my husband took the kids to the Not So Scary Boo Parade and I took the littlest ones back to the hotel. Definitely have a stroller...if you are bringing one for the youngest you might consider renting one for the 2 older girls. Its a lot of walking for a 5 year old and it was worth everypenny (the one we brought got a flat and couldn't be fixed I was thankful in the end because we didn't have to haul it on the bus to the park.) Everyone working at these parks make special effort to see that even the littlest ones has a good time. My daughter slipped near some management types who were preparing for the evening activity and the whole group came running over and went beyond the call of duty to make sure she was ok. Its a magic place for little ones. We loved Magic Kingdom, Animal Kingdom, Universal Studios and Epcot Center and the pools back at the hotel.
Goodness, they will probably sleep all the way back to Texas afterwards. They'll be so tired (and you might too) but you will have great memories. Its worth every penny and you can make it as stressful or not as you want. Use the planning materials they send you from Disney...they do a good job orienting you.