Are you renting a houseboat or getting a hotel room each night?
If just day tripping and you don't want to go too far up lake (it does get rough mid day if it's a holiday weekend or a wind storm kicks up) or through the 'narrows' try a day trip to Navajo Canyon.
If you go to Rainbow go early in the morning and hit Dangling Rope for fuel both directions, then you can enjoy some of the side canyons on the way home. I recommend seeing the rest of Forbidding Canyon ( the canyon that Rainbow is in, turn left when departing after the tight squeeze where the rainbow bridge sign is) and Cathedral (first canyon down stream of Forbidding) on your way back to DR for fuel and ice cream. It's not a long day if you start early. Take a lunch to enjoy while idling through the canyons.
When are you going? I won't go back up until the crowds leave. We enjoy it Sept - Nov. We have the lake to ourselfs.
The Onion Rings at the Wahweap Marina restaurant rock
Once you get north of Gunsight the lake really calms down and the beauty begins. Sad fact is sometimes you have to put up with some rough water (go early) we call the Maytag Straits due to the vertical walls on each side of the channel do not dissipate wave but bounce them back.
Once again, if you are running up to Rainbow GO EARLY. Way before the tour boats run. If you see a tour boat coming your way, get as far away as possible and approach their wake at 45* slowly. The wakes are HUGE.