Best Friends is an awesome facility. They have a couple RV sites in a gorgeous area. Reserve now!
From Kanab check out nearby Coral Pink Sands State Park. The color is beautiful. Also nearby is Pipe Spring Nat'l Monument. You could do a day trip to Zion but a long day. In my opinion, Bryce is too far for a day trip.
From Kanab I'd highly suggest you go to the North Rim of the Grand Canyon for a day trip. Have lunch at the Lodge overlooking the canyon and just outside the Lodge starts an easy trail out to a point overlooking the canyon. It doesn't sound like you're experienced heavy-duty hikers so you shouldn't even try hiking down to the river. It's a very demanding, difficult hike - even down! However, I do suggest you at least walk 1/8 or 1/4 mile down to get an altogether different feel of the canyon.