When we have gone to WDW as an all ages group, breaks are often appreciated by the youngest and eldest.
If the 2 year old isn't tall enough to ride, in most cases, CM's won't let them enter the queue.
Also, it might be helpful to note quiet waiting spots like the little playground by Splash Mtn/BTMRR. It has seats, shade, and a cute little playground for the 2year old. There's another one located in the post-ride area of Mission: Space with a playground, seats, and air conditioning.
Personally, I don't find the pre-ride of M:S, BTMRR, or Splash all that exciting.
WDW's full of little relaxing spots if you know where to look.
A really fun one for little kids is over by Kali River. First, there's a fun splash fountain area. Second, there's the Tiger Trek. We've split up many times, and much prefer these options.
if you need more...I can keep going..for SpaceMtn- the non-riders go on the Peoplemover, get a snack, and/or use the bathroom.
By RNRC, there is - or at least there used to be a kid area. They gave kids a paper and stickers to put allover the paper. I'm not sure they still offer those, but it was cute. We also got some fun shots at a Photopass stop in the area too, but I don't think the Photopass photgraphers are always in the area.
Another common option for us, was to send part of the group to see the nearest (or most interesting nearby) show. Tomorrowland sometimes has one. The World Showcase is full of awesome performers in the afternoon.
Many rides- including RNRC -also have a gift shop. An inexpensive item we sometimes bought in the RNRC gift shop (and others) was a pressed penny.
Still one more option...if your family is into the idea....get the Hidden Mickey guide book. Your non-riders can do a scavenger hunt for hidden Mickey's. they are all over WDW: queues, rides, gift shops, even the hotels!