As noted by iLounge, Apple has started selling "iPad Gift Cards" in its retail stores right ahead of Christmas. The cards aren't anything special -- actually, they're just standard Apple gift cards wrapped inside a nice iPad-specific package.
What's interesting is that, apparently, Apple updated its iPad purchase policies to include support for discounts through the aforementioned gift cards. Until a few weeks ago, Apple only allowed customers to buy an iPad via a debit or credit card.
Now you don't have excuses anymore: your wife wants an iPad. You know what to do.