Can someone refresh my memory as to how the baby swap works on the fastpass rides? There will be three of us, not counting the baby, do we get three fastpasses and then tell the attendent we want to do a baby swap when we arrive at the assigned time?

Okay, this is verbatim from an Indiana Jones Rider Switch Passport:

This pass is good for TWO people

1. One or two adults wait outside with the child that does not meet the 46" height requirement. The rest of your party waits in line.

2. After the first group rides they watch the children.

3. The adults who waited then proceed through the FASTPASS entrance using this pass.

This pass is only good on the day it is issued.

While waiting you may wish to visit Tarzan's Tree House or the Jungle Cruise.

~~~~~~~~~~~~~

Okay, that said....here's what we do:

We grab fastpasses with every park hopper we have (even the child who is too small to ride), and one person gets in line with the kids who can ride and grabs a switch pass for the waiting adult.

So now the first adult has ridden, and the kids who can ride have ridden once.

The second adult rides with the switch pass and one of the kids who are tall enough.

Later, when we use the fastpasses, the adult who goes in first grabs another switch pass for the waiting adult, then the other adult uses the swich pass and can take all the kids using the s.p. and the remaining fastpasses. (We have three kids, one who isn't tall enough for Indy yet, and it gets hard to tell the older two kids that not both of them can ride with us on the switch pass...picking and choosing who gets to ride when is terrible.)

I am not a parent, but have read enough to know that the procedures are different in DL and WDW (and given the signature of the OP, I'm guessing they're going where there is no Indiana Jones with a height restriction) - and they can be different at different attractions.

Edited to add:
Ok, I went back and looked again -and SOMEONE is going to both parks! Maybe you could clarify which you're asking about!

Basicly, your whole party goes up to the FastPass entrance and asks for a rider swap.
From there, if you have a fastpass for that attraction, those who are riding can go through. Others stay with the young ones. If you do not have a FP for that attraction, just wait in line with everyone else.
Once your ride is complete, the ones with the rider swap pass can enter the ride via the FP line while you stay with the young ones. IIRC, for most attractions, the holder of the rider swap FP can take like two or three people with them through the FP line. Yes, even a person who just finished the ride. (My daughter loves that.)

I did a little search and here (http://mousepad.mouseplanet.com/showthread.php?t=12925&highlight=rider+swap) is a link to a past thread that has some good rider swap info. A search on "rider swap," "baby swap," or "child swap" will produce even more help and tips.