I have taken my four, now 15, 14, 12 and 10 alone since the oldest two were 2 and 3. It really works out well at Disney. Since the majority of rides are those that everyone will ride, it really doesn't create a lot of downtime. Plus, with the new Fastpass system, it is easy to go in and change two fastpasses for your older children to one ride and one for yourself and your four year old to another. We have done this a few times. I will get them fastpasses at one ride, and fastasses for me and the two younger ones at a ride really close by for the same time. Then we point out a meet up location and go on our respective rides alone. It is absolutely doable, and you will have a ton of fun!