Grand Canyon - We have visited probably a dozen times over the years. We either stay at Bright Angel or camp in a tent. Both are fun and have their advantages. If you can, hike down to Phantom Ranch and stay the night. To make a day of reservation, go into Bright Angel, go to the left of the main desk and talk to the people behind the tour desk. They usually have a cancellation or two at Phantom Ranch every day. They will try to deter you at first but if youre persistent, they will find a spot for you. Its an incredible experience. Hike down the Kaibab trail, stay the night, then hike back up the Bright Angel Trail. Make sure you walk the rim trail and go into all of the shops and museums. I love the Kolb house. Get on the bus and ride it from one end to the other. All the different views are amazing. Watch tower is awesome. Make sure you time it so you are at the sunset point at sunset. its an amazing view.
Zion - We went last year and it was really great. We camped in a tent and hung out at the Zion Lodge in between hikes. The Narrows is a must do. Its different than any other hike I have been on. We didnt get to do Angel's Landing as it was closed but I have heard its amazing. We did several other hikes including the longest one up to the tallest point but I cant remember the name of it. It was a great hike and the view at the end was awesome. The little town next door is really nice and we walked in for dinner on a couple of occasions. The bus system to get around is really awesome. Try to catch a ranger talk or two if you can. They are really good.
Bryce Canyon - I was really surprised by this one. It is not as big or overwhelming as the GC or even Zion but it is more intimate and just so unique in the landscapes. The hikes are really great and the views are just hard to beat. We tent camped and had a great time. We did a ranger talk and did the night sky viewing with the rangers as well. We really enjoyed Bryce Canyon a lot. We did the longest hike from one side to the other and got to experience the canyon and all of the interior views. Make sure you drive along the rim from one end to the other. The views are all different and amazing. The pizza place next to the main lodge is really good.
Its a beautiful drive going from one to the next.