Well, the single rider lines should be used ONLY if you are fine with riding alone. It will be good for us, a family of 3 with a 3 year old, b/c I can run over to CA Screamin' and do the Single Rider line to get on and off very quickly, while hubby and son do something else.
In fact, for us, even swapping out, while using the Single Rider line, would work, and would probably be faster than doing the official rider switch baby swap kid swap whatever it's called. Because it's ONLY one adult riding it each time.
But since you have other kids, some of whom are able to ride restricted rides, then the swap/switch pass is better. No one will get split up into different cars or entirely different ride cycles like with the single rider line, AND you can take more people in with you on the swap/switch.
Say you go to Indy. You stay behind with the little ones who can't ride. The other adults and taller kids go on (either with a Fast Pass or in the standby line), stopping to get a swap/switch pass when they get to the CM. (we have only been there at relatively slow times, so far, so the CM is pretty much at the beginning of the line and we haven't all had to stand in line until getting the pass...at a busier time the line is longer outside, and so you might need to get in line with everyone until you reach that CM) (this is all more confusing to type out than to DO)
So the first group is in the line, having gotten the pass. When we did it, the first riders just kept the pass, but if everyone was in line until the CM gave out the pass, the second rider(s) could keep it I suppose. The person with the little ones hangs out...grabs a snack, walks up in the Tarzan Treehouse (remember I'm talking about Indy here), shop a bit, or just sit and rest.
Then the first riders come out, and the other adult gets to go on, AND can take others along! I know there's a limit, but with Indy, I only dragged one person along with me, and that won't happen again b/c my brother and SIL can only go on Indy one time without hurting.
So the second rider group takes the pass and goes through the correct line, which the CM will tell you about. For us, at the time that we did this, we went in the exit, which was fun until it meets up with the normal line.
OK that got wordy! I only hope that there was a glimmer of help in there amongst the words. I always do this when watching pirates of the caribbean while typing...we should all be glad I didn't start "talking" like Jack Sparrow...
Main points...single rider line is for when just ONE person wants to go on something, or you have a very small group like ours and taking turns won't take too long.
Not every ride has single rider.
Rider switch/baby swap is good b/c more than one person can go on the second round, and people can even re-ride if the group is small enough.