We are definitely going to be doing this on our trip. Looks like you do have to stand in line and be directed to a 'waiting' area? Here is the info and link for a list of rides this is offered on
RIDER SWITCH / SINGLE RIDERS
You're at one of Disney's theme parks and you have someone with you who doesn't meet the height requirements of the attractions. Does this mean that you're doomed to riding Small World over and over and over....?
Luckily, at Disney World you and the others you're traveling with can "swap" your child and take turns enjoying the rides without having to get back on the line. (And no matter how cranky your kid is, this doesn't mean you get to trade for another one.)
First, check that it's offered at that particular theme park attraction. The Disney Cast Member will then instruct you to enter the queue. Once you're at the boarding area, let the Cast Member know that you want to "child swap." They'll show you where to wait while the rest of your party enjoys the ride. Once they get back, you hand the little guy over to them and you get your turn without having to get back on the line.
This works best with kids who are too young to be aware of what's going on. It may not be the best plan if you have a 3 year old and everyone else gets to ride. They know that they're missing something and could be quite vocal about it.
Two attractions offer another option, a separate Single Rider queue. This usually moves faster than the standby line and is a great alternative if you don't have a Fast Pass for that attraction and don't mind riding alone. This is offered at Test Track and Expedition Everest
http://www.wdwinfo.com/childswap.htm