I also love to share what my favorite sets are, here are my 5 favorites for the range that you mentioned:
1. 8038 Battle of Endor
EXTREMELY fun set, lots of cute little features - definitely worth $100.
2. 10178-1: Motorized Walking AT-AT
I don't personally own this set, but it has a lot of good reviews and is quite a classic...
3. 7754-1: Home One Mon Calimari Star Cruiser
Its a cute little play set, definitely another good choice.
4. 8098 Clone Turbo Tank
If your son is a Clone Wars fan, this is a great set -- the turbo tank has flexible suspension (yay) and two rare figures.
5. 8081 ARC-170 Starfighter
This one really is a fun build. And it comes with the epic pilot figures, and Kit Fisto which is a plus.
There you go, good luck choosing