I've bought several skylanders year using GCU. I've read on unboxed somewhere, its tied to the SKU, which alot of them share, but "Mike" was confident that it wouldn't affect anything since they're listed as different items sharing the same SKU.
And Brian made a post on 8/7, clarifying the...
http://www.bestbuy.com/site/promo/select-title-offer-123276
http://www.bestbuy.com/site/promo/pre-order-titles-123276/category_facet=abcat0700000?qp=category_facet=Video%20Games~abcat0700000&nrp=15&seeAll=
Links to both the preorder games, and the list of ten games to choose from.
I picked a 2ds up last time they had the sale, They were sold out of the pokemon bundle but the guy in electronics gave me a regular one and the psychical copy of the game together for the sale price of 99.99. YMMV but it never hurts to ask.
For games, yes, Theres a twenty off of The Last of us, and ten off of Kingdom hearts 1.5, 32 for TLoU, and 16 for KH1.5, Online it stacks atleast, Also, it comes off after the coupon.