Boofer,
As this hasn't been mentioned, I thought I would throw my 2 cents in ..
Consider the Citibank Dividends Card. 5% in gas, grocery, and drug stores. Max of $300 in rebates per year. You receive a check automatically with $100 in dividends saved, or you can request a check even at the $50 level. It is a check made out to you, so you can spend it or save it any way you like. If you are married, get a separate account for your wife .. and now your max. is $600 because the accounts are not linked.
I still use the SPG amex becuase it suits my purposes best, but my family members (old and young) have all gotten this Dividends card and are happy with it. They have even gotten the checks as stated in the above paragraph.
I would also caution you to consider the possiblility of higher fees or mandatory minimum investments with the Upromise funds. As I don't have kids I haven't looked much into it, but I seem to remember that I found the fees and minimums to be a bit high, as I was looking for beneficiary gifts for nephews/nieces/etc.
But the Upromise card is really worthwhile if you shop at grocery stores such as Randall's where you have to use a "Member" card in order to receive the discounts in-store .. then through the linkage to that "Member" shopper card, purchases of Upromise groceries such as Land-o-lakes Butter are added to your Upromise account automatically.
Their iDine program is worthwhile if you are not using the card attached to a FF account.
In the end, it looks like you will need to look into getting at least 1-2 cards to maximize your potential because of the spending limits.
Rob.