My personal opinion on the Grand Canyon is this...
1. If it's your first trip, you probably want the south rim. While I like the north rim best, there is much more to see and do on the south side. Most of the classic images are from the south side.
2. If there is any way to go to the south side other than in June, July and August, its better.... June-Aug can be a zoo. But, still....refer to # 1 above.
3. Even if you are not a hard core hiker....go at least a little way down below the rim on one of the trails. It's a whole new experience down inside. Just know your limits and ability to climb back out...but even a short distance down gives you a taste.