I work at JAWS, and it does have posted warnings for pregnant women, as well as for back neck and heart conditions etc... The ride can be rather jerky (depending on which boat you end up on), but not near the level of Back To The Future. There are some loud and startling effects.
This is kind of like the question I get all of the time when I'm out at greeter. "Is this ride too scary for my kid?" Everyone has different reactions, and physical limitations. I would recommend that you ride first, and judge for yourself. I won't guarantee anything, but if you ride during a slow time, you can try asking the load attendant if Rolls can be disabled for your boat.
The best time to ride is before/during a "Wild West" stunt show. That is when our lines are shortest. Especially before the first show, since most people who have worked their way to the back of the park that early go to the West show.
Conversely, the WORST time to try to ride JAWS (and MIB) is right after a West show since half the people in the theater come to JAWS or MIB. In less than five minutes time we can go from a 5-10 minute wait to a 45-50 minute wait.