This is pretty much a classic risk assessment.
You don't say what government money you are expecting, but considering the cost of a WDW vacation, it could be tax money. In that case keep a close eye on your online account at CRA. Refund/payment status is often posted there a bit before the money comes in. If it is payroll money from the Phoenix system, all bets are off. I have coworkers who are still limping along without their spouses salary.
If you are assured of the payment in a reasonable time, I would suggest just floating it on credit. If the money still doesn't come through in time to pay the bill, the carrying charges on the expense may still be less than the cost of cancelling. Unforeseen circumstances like this are a good reason to use a CC to cover the gap.
Other than that, I would look to the cancellation costs and bail before the risk got higher than I feel I can afford. You only mention a hotel risk above, so if that is the only cost risk (no airline tickets? Cancellation of leave at work so you don't lose shifts? Anything else?), then I would wait until about 48 hours before to call it. The kids will be just as disappointed regardless of when you cancel, but won't be disappointed if you go through.
