and to add on to the kid swap tip.....
if the ride/attraction is one where you want/need to utilize fast pass, be sure to get a fast pass for each ticketed person in your group (obviously you can't get one for a kid under the age where you don't need a ticket to get into the park). when your fast pass time window arrives go to the fast pass entrance line with everyone in your party and your fastpasses. they will collect the fastpasses for the group and then give you your child swap pass.
also - note that this is sometimes a problem with Soarin. you can't take a stroller in that building, so you have to take the baby out of the stroller, go in and collect the fastpasses for everyone, then take them out again if you leave and return at your fast pass time. bummer, but you can deal with it if you know about it up front.