My guess would be to accept the financial aid. The money won't get disbursed until the start of school anyway, so if you withdraw, then the loans would never get disbursed. You can't generally transfer loans from one institution to another. This might be possible with private educational loans though, so if you are going that route I would check with your lender. For direct loans though, if you don't register and enroll at the school, you don't get the money. Even if you enroll and then withdraw (say you get off a waitlist somewhere on the second day of school and decide to take it), then all you will need to do is give the money back if you already have it in hand.
You could also call the school and ask about accepting the award. If you don't want to mention the waitlist, just go with the "family emergency" excuse and say the you plan to enroll, but there has been a family emergency, so there is a chance you won't be able to, and ask what would happen if you accept the financial aid award now and then need to defer or cancel enrollment in the fall. The answer should be the same if you were not to enroll for any reason including a better offer from a better school.