Would it be Ok if I waited for another couple of weeks before I dropped some candy in there? Or should I do it sooner since they're already in the top box?
Hard to say if it is ok to wait another two weeks.
Without blowing smoke, which happens by all the experts everytime someone mentions feeding, my best advice would be....Go ahead and place the feed on them. Nothing sucks more than losing your hives the first year, especially for something such as a lack of food, and something so easily handled.
The key of why I would not wait, is the fact that your bees are in the top box. Many times this is due to the bees feeding up through and having limited feed, while also trying to conserve energy by placing themselves where trapped heat helps them the most. I would place fondant/candy/sugar on the inner cover hole. Here is a page on feeding sugar: http://www.pennapic.org/feedingsugar.html
Disclaimer: I have been told that my advice, and the feeding practices mentoned above are "child's play" and that "Americans are ignorant when it comes to feeding". Please be advised that such claims if seen after this post will not be responded too. We offer the above advise without malice, ill-will, motive, ego driven agenda, or negative connotations. It is offered by us with no expectations, and your acceptance is of your free will. (signed-An ignorant American)
That is all.