Some people may say 15 months is just to young to bring a child to Disney and I highly disagree! Also since you have an older child going as well, that child will be a great role model for the 15 month old through-out the trip. My husband and I previously took our 12 months old last October. You would be surprised how much she got out of that trip, it was AMAZING! Character encounters.. don't let people tell you their to young for that too.. my daughter never wanted her turn with the characters to end!! Tips wise- I would say to bring your own stroller and a bulky, luxury, style one at that. We have a Jeep Stroller, very nice, reclines fully back, has a full visor over head for shade, has air venting all over so when the visor is over the baby wouldn't get hot and it has a TON of storage space, which worked out awsome while shopping in the parks! But mostly bring that type of stroller for napping, your child may want a bottle while at the park, give the bottle to your child in the stroller and keep going.. he will probably pass out and let your 7 year old enjoy her time. Our daughter would pass out for a hour and a half everyday, we never had to go back to the resort for nap time, but I know every child is different. Eating wise, yes make sure you DO make time to always stop and have a meal, sit down, don't rush it.. even if it's quick service.. take some time sit down at a table around and eat your meals and talk about your day.. this will give you all a break but mostly your youngest who will need the biggest break. Changing rooms- you'll find them all over the park, no worries on that.. and the Mens restrooms have them as well, it's a nice break for the moms! I would say to pick and choose what shows though, if your doing some.. because those are a hit or miss at that age. The attractions are all great for any age, but the shows can be hard that young.. we only went to a few because we found it hard for her to want to sit and watch one through or end up screaming half way through LOL. Some say use one DW trip for attractions and another trip for DW shows.. theres so many of each this may be true. However she did do awsome during some shows so young, like Crush in turtle talk.. Nemo.. things like that. Things will be at a slower pace, and I know it's disney BUT don't worry about seeing it all.. enjoy your family time and hit the most musts and then conitune from there. ENJOY!