hi Mama2tori,
The Safari is relatively bumpy in several spots, and I did notice on my last trip that there is a sign discouraging pregnant women from riding.
There will most definitely be signs warning you before you get on other questionable rides. I don't think you'll be sitting out on a heck of a lot of rides. Basically you'd be stuck sitting out of the thrill rides. There's plenty else for you to do. Because of back problems (ok, and because I'm a wimp!), I end up sitting out on the thrill rides, but have never found myself bored at WDW. We get fast passes for my DH for the rides that are "must dos" for him, and the time I spend waiting is pretty minimal.
If your DH is interested in riding the thrill attractions, he may be able to get on in a relatively short amount of time by doing the Fast Pass, by going through the single rider line, or by telling the CM at the attraction that he is willing to ride single.
Bring lots of water - rest when it gets hot (go back to the room and have a nap) and most important, have a great time! By the way....welcome to the DIS boards!
Kim