My 11 year-old son loves Heroscape but he's also been playing it for a couple of years. It is a lot of fun.
I've been thinking of Heroscape too, I'm just not sure if it's going to be enough of a challenge for him. I've also had some thoughts about possibly getting him Carsaconne since he's taken some interest in the XBLA game.
The great thing about HeroScape is how you can change the board however you want to. Not only that, but it does have pre-set scenarios that you can use or you can make them up. If you are worried about challenge for him, you can handicap one side or the other by how many points they are allowed to spend on characters. With all the characters available, you can create a lot of unique armies. It also has some sci-fi characters and some fantasy characters, as well as some that are more "realistic" like Western gunslingers and WWII soldiers.
Also, you can always buy expansions later to change things up a bit. Granted, that can get expensive and create a need for more room later (I have two tackleboxes that I use just for the characters I bought), but they have usually done a good with the new characters.
That would be the best option that I can think of now, but I haven't played the games you've mentioned.