If you haul your raft on a trailer you can't back it to the water between 9 am and 4:30pm at Grizzley Creek. Reportedly there were a couple of "close calls" where the bikepath crosses the access to the boatramp and the USFS decided to close the ramp to trailers during prime summer launching time.
Its a great float, has some splashy Class II that'll be fun, spectacular scenery, and the highway's not as obtrusive as one would expect. Depending on the water level the hotsprings on river L about a half mile above GWS may be in. If your boat's easy to carry you could launch at Shoshone, hit the fun Class III section, and pick the rest fo the family a mile downstream at Grizzley.
Have a good trip,
Nothing in the world is more yielding and gentle than water. Yet it has no equal for conquering the resistant and tough. The flexible can overcome the unbending; the soft can overcome the hard. - Lao Tse