You can totally do it. I go alone with 21 month old trio but don't do autopia because of the risk of a bump and injury.

Do you live close to D-land or is this a vacation? If you live close, or even if you don't and can plan accordingly, go on a weekday first thing in the morning. The lines are shorter (or nonexistent). If you must go on a busy day, plan ahead and get the fastpass at the start of each of the lines you want to ride (in your case you'll get 3 total), get your ticket and return to the ride at your designated time (the ticket/pass) will give you a time. One of you can take a kid on the ride while the other two watch, and then switch off. If you use your FastPass and explain your situation they may let you just transfer kids and the parent won't have to get off ride (unless you two want to switch off too). Does that make sense?

Have a blast!!