I enjoy collecting as much as anyone (been at it for 27 yrs) and I probably will buy some of the figures just to have because they are pretty nice figures overall. The power discs, not so much. To me those are typical game DLC type content and without an enhancement to the game experience are basically useless. If I do get into the Toy Box I may buy some individual textures and such off ebay but I can't see buying blind packs (I hate blind packs on general principle anyway).
As for the age thing, this is rated at the same level as the Lego games so I figured since he's good at those then this should be good for him as well. Also my mother was kindergarden teacher and many of her kids played Skylanders. So I figured he was the right age group for this game. Heck in Lego LOTR he completed start to finish several levels on his own without my help at all. I think this comes down a few things for him. The DI camera is not as good as the Lego camera (especially in 2 player, which is what we play most of the time) causing him to fall off buildings, get loast, etc and the control scheme has issues. Although I have little to no issues with the platforming he does struggle with it sometimes and I have noticed that some times the controls don't respond or the camera changes to a funky angle at the wrong time. Last night I did some Monsters stuff and all of a sudden I couldn't do the wall jump on a section of wall I just used a minute previously (I fell off trying to make a jump). His other issue is he is still learning to read and there is a lot of text in this game. learning to read has been frustrating for him and think this carries over. His math and problem solving are much better.
He also seems to like games with clear levels more (Lego, Mario). At times he doesn't like having to go find a mission all the time. Again my hope is future play sets provide different types of games. I'm fine with the starter pack being similar as an introduction but the add on play sets could be different.
Also I messed with the toy box a little just to see and since I've played a decent amount of the game I have unlocked a lot of toys. Trying to find them however was a pain. I hope through a software upgrade or something they make it easier to find the toys. Even if they are sorted by type (cars, people, walls, etc) that would help me. It took me about 10 minutes to find the toy I was looking for.