We just got back a few hours ago from our first trip to the Vegas/Grand Canyon area (which is why I'm still up...the 3 hour time difference has me all screwed up). Our family consists of DH and I (both 48), DD (almost 18), DD (almost 16) and DS (13 1/2). Included in our trip was two nights at the Lake Powell Resort and Marina, with a 1/2 day smooth water raft trip down the Colorado River...a highlight of the trip.
http://www.riveradventures.com/ Our tourguide was a really great 19 yr old college sophomore...funny and interesting...and it's the type of thing where you bond with your raftmates. (As a matter of fact, one family on our raft of 20 is from the next town from us in RI AND the grandfather was my boss years ago!)
We also stayed at The Grand Canyon Railway and Resort hotel, and took the train to the Grand Canyon, spending a night at Maswik Lodge on the South Rim. Both accommodations were very charming.
http://www.thetrain.com/ We also loved the train ride experience (we had dome accommodations)...singing cowboys, funny waitresses, beautiful scenery, and on the way back, masked cowboys taking over the train, which little kids on the train especially enjoyed!
We drove through Zion National Park, heading from Lake Powell to Las Vegas, and it was gorgeous, but I have height issues, and it was a little nervewracking for me, as were parts of being at the Grand Canyon. Both absolutely breathtakingly beautiful tho.
We took a ride through The Petrified Forest...not worth the detour we took, IMHO. Also took a quickie stop at Lake Mead on our daytrip to Hoover Dam.
We were doing more sight-seeing than hiking, but I hope this helps a bit.
Look into getting a National Park Pass. We didn't (we spontaneously made some of our detours to parks), until the end, when we managed to have $50 in park receipts. For ex, it was $5 to get into Lake Mead, $15 for Lake Powell, $10 for The Petrified Forest, and then we traded them in when we were entering Zion National Park because that cost $20...so we had $50 worth of park entrances. However, Hoover Dam had a fee (we couldn't find our receipts), as did Grand Canyon, altho it was included in a package...therefore, no receipt; if you get the pass, you might be able to have that portion of any Grand Canyon package excluded.
http://www.nationalparks.org/Home.asp
I did NO planning for this trip, due to so many other family things going on this year, so the trip was planned by DH and a
travel agent, but if I can answer any questions, I'd be happy to help. There were some things I would have liked to have done, but we did a lot of driving, and sometimes just wanted to get where we were going!