We just did this a couple weeks ago. What you want is called the Rider Switch Pass, but if you ask for a child swap pass, that'll work, too. They do this all the time.
I was instructed to wait with the little one in the EE gift shop, which is where the ride lets out at the end. Once my two guys got off the ride, we easily found them, and then I rode with my guy while DH waited with our little one. (Note: the ride broke down while we were on it and we had to be 'rescued' by the CMs and led down into the inner sanctum of EE, but that's a different story altogether. We weren't scared. It was cool!)
BTW: We used this same strategy on numerous rides in the parks with never a problem. The one thing that was confusing was in Space Mountain, and the instructions were for us to take a back way exit down a flight of stairs and wait. I just had trouble hearing the instructions because it was noisy. Anyway, we got there, and it was the end of the ride, and we just waited on a bench. When we did the switch, we walked up the same exit we had gone down, and there we were. It was still very easy.
Our DGD is 6 years old, so we wondered if anyone would give us grief in asking for the Rider Switch Pass, but they never did. They handed them out without a word at the head of the line. You get specific instructions from the next CM down the queue.
Have a great time.
Grmammy