Well, I'm not average, so I'm not worried about that "hidden" cost. A credit card has no impact on my spending, it's just another method of paying for things.
More generally speaking, I would suspect the average 529 account holder isn't an average credit card consumer either.
That is, someone who's planning ahead for college savings is probably more likely than most to be paying off their credit card bill in full every month.
So I wonder where the 2% is coming from... the fee charged by the CC companies to merchants would just barely cover that. Maybe Fidelity is kicking in some too.
Like russellt, MBNA isn't my favorite company, and I've also been a long-time customer. They are terrible telemarketers and junk-mailers, it took me forever to get completely removed from their lists (two separate cards, only one by choice, the other by buyout).
And with my last MBNA bill, the payment stub has been changed to no longer show the full balance due -- just the minimum amount! To find the full balance you have to look for the fine print at the bottom of your bill. I'm sure it was just an oversight on their part.