Just make sure the contract is very clear on exactly which exchange rate you'll be using and at what time. Imagine you agree on a deadline of Friday at midnight for some project. The contractor delivers the finished job and final invoice to you on Friday 4 pm, but you don't get around to handling his invoice until next Wednesday at 11 am. Which exchange rate will you use? The answer to that question could be worth several thousand dollars to one of you, so it's not a question to take lightly or assume that it won't cause massive potential headaches for you.
At this point the plan would be to keep a small amount of USD in Mt.Gox and buy bitcoin at a set time and send immediately when payment is due.
This is all new to me, but it seems like a reasonable plan at this point. So if I'm missing something silly here let me know! Thanks