If you do the Visa GCs, can you get them fee free as a result of a sale? I wouldn't be buying them if you're paying the activation fee versus DGC being fee free. I know the Staples fee free sales aren't for a couple of weeks, since Visa just happened...
Do you have to hit the welcome bonus before the trip? Only asking because you said the trip is in a couple of weeks, not sure how tight you are on the bonus time frame.
If you have to make prepayments, I would buy DGC for a bit less than what you expect you'll need so you don't end up saddled with extra Disney money you don't need to spend. I'd also see if there are any other expenses you can prepay now (can you call and pay a hotel early, can you switch to a prepaid rental car, etc) so that you're spending the real amounts you need to versus guessing on gift cards and accidentally overshooting.