We've been there with our dd's from as early on as 16 mos. (she is now 9) and our last trip their ages were 5, 9 and 11. We have faced many of the issues I have seen addressed here. The gimmes, the meltdowns (due to being overtired), the time outs (we too have used the bathroom as a "Take 5" staging area -- much to my dismay my then 4 yo even found THAT fascinating! LOL). I have learned to just follow their lead for a lot of the trip. I do plan ahead, but since they are much older now I am also able to pull out a book or hop online and let them help put our day together. We each created a 'Wish Book', what we WISH our trip could be like ... I reminded them continuously that sometimes wishes don't come true, but it sure is nice if they do!!! It was great when we returned home and many of those wishes did in fact come true and those that didnt got transferred over for the next time.
Our approach is to set forth guidelines and expectations of behaviors ahead of time (and they KNOW I stick to my word, so if I say we are Taking 5 in the nearest bathroom I'll do it). The gimmes are controlled by handing them their envelope of Disney Dollars to do with as they see fit, however, I always advise them to look around and see all there is to offer first. I also tell them it is best to shop at the end of the day or so otherwise things could get lost as we go on rides, etc. This has never been an issue since I do hold true to my word. There were days they would spend over $30 in one day and other days they would only spend $5. I buy snacks, etc, they buy their 'trinkets' and souvenirs. Meltdowns have happened, but I am quick to divert attention by coming down to them and letting them know that I cannot help them if they cannot calm down enough for me to do so. I have often sat on the ground with my little one in my arms until she could just settle down and let her know in soothing tones that I would help her just as soon as I could understand her, but until then there was nothing I can do. She quickly understood that I wasnt fighting her, but willing to help and then piped up with her 'demands' so to speak! LOL Sometimes they were things we really couldnt do and the crying jag would start again, and we'd go through the whole thing again until I would expalin, I didn't say NO, I just said Not Yet (she wanted to ride on something that had a height restriction), well we added that to her Wish Book (she was an itty bitty thing), and the next time we went down to WDW that was one of the FIRST things we did!!! She was tall enough for the Barn Stormer!!!! Yaayyy!!! LOL We are very laid back about food and such, since they are very good eaters at home we just kind of let them go for it while there (within reason). Thankfully they are not junk food-aholics (who's kids are these?!?!) like I could be LOL so that was also not that big a deal. Our Wish Books have really often times saved us sanity, I put some cool clip art in it, we would add glitter to it and even foam shapes and such glued to the cover and it would sometimes keep them busy as we stood online or waited for a Fast Pass. Having them each take turns in deciding what we do next also helped. They each also got to pick where we ate one day, again giving them a sense that what they say DOES matter. But I often reminded them that I will try to get things done with them all, as long as we work TOGETHER! When our little one was stroller bound our rule always was that the other two had to have their hand on the stroller to either side of me. This has been life long for us though since we live in NYC and are often on the subway. I miss that stroller!!! Now I can only hold 2 of them and my oldest is my 'shepherd', she helps keep them in line etc LOL But I still worry about her, although she knows the subway as well as I do by now! My dh is great when we are at WDW because we have the same parenting style, thankfully. So when he sees that someone is approaching a scary moment, he either hands off to me or quickly jumps in and tries to to difuse the situation. So far, so good.
Our last trip was March 30 - April 7 of this year and it was a surprise trip that the girls knew NOTHING about so their Wish Books were left behind (or so they thought), I had stashed them in the bag, so they worked on them during our flight down. We had eagerly been planning our upcoming June trip, so their ONE wish that the trip would be SOONER really DID come true!!!!!! Anyway, enough babbling from me ... All that matters is that everyone have some input and as far as naps go, we noticed when our little ones were younger, they would often just collapse where ever we were!!! LOL We have more pictures of our youngest sleeping while we are on vacation than anything else! LOL Enjoy! Enjoy! Enjoy! Remember, it IS the Happiest Place on Earth ...