OP, this is a good question. Let us know how it turned out when you have a chance.

I'm in same situation. Cancelling a Friday flight and hoping the credit reissues quasi-immediately to rebook a flight for next week. I'm either too close in for the hold function at this point or it's not offered as an option.

My previous experience is that it's usually pretty quick. But unfortunately, AA is not known for its consistency lately. And re-using flight and trip credits seems to come with its own set of whacky nuances. Recently I ended up with a paper voucher because the agent said I'd reused the credit too many times.