FP+ with AP voucher and hotel res?

[DopeyDame]

We have vouchers for APs bought through AAA. We will also be making hotel reservations for sometime in September in the next week or so. I tried to link my voucher to MDE, but it says the code number is invalid, which makes sense since it's not a real ticket.
However, does that mean we won't be able to prebook any FP+s since we won't technically have a valid ticket until we get to WDW and exchange the voucher for the real deal? Any way around that?

Thanks!