We went in May with my mom (69), sis (41), DS (11), DD (almost 3), DS (1-1/2). DH and I are in our 30's.
My mom has a lot of endurance, but at the start, we basically told her and my sister that we get up at the crack of dawn, start early, come back for down time in the early afternoon, and then go til 9-ish. They pretty much did everything with us. My mom would take a break, lying down and reading or a nap when the little ones did. During that time, DH and I stayed in the room, although he did go out and do a little shopping at DTD one day. My sister and DS stayed in a couple of the days, went swimming a couple of the days, and stayed at the park another day. On the day we went to blizzard beach, mom went to DTD and shopped, had lunch, and relaxed. The evening, she went to dinner with us and to the park.
If we didn't have the little ones with us, I would have just told them we go all day, but they did not HAVE to join us. I think if you lay that out up front, you will be good to go. If your 3 yr old niece goes back for a nap, or your stepdad and mom want a break, they can go back and do that. If you guys want a break, let them know that they can do whatever they want. My sister is not a morning person by nature, but she did get up and go early. We constantly reminded her that she could join us later if she wanted. One morning she was beat, so she slept in while we had breakfast at O'hana and then joined us at MK mid-morning.
I could tell my sister and mom seemed to think they needed to do everything with us, since we paid for the room and everything, but after we reminded them 100 times this was their vacation and if they chose to blow us off and go drinking, they were free to do so, they seemed to do a few things on their own.
They must have been okay with the arrangement, because guess who is joining us on our 2 week February trip???
One mistake I made was trying to PLAN for what everyone might want to do. It ended up exhausting me and when we came home I felt like I had been at work, not on vacation. not this time. For Feb, I typed up our rough itinerary (we basically plan what park in the morning, which in the afternoon, and our character and special meals). I gave it to my mom and my sister, along with the guidebooks and they are going through it, deciding what they want to do WITH us and making their own plans for when they don't want to go with us.
