As with most things, it depends largely on the location...and who's at the counter...and how their feeling that day.

I was attending a wedding a couple of summers ago, and booked two vehicles with National at YYT.

The only issue National had with me taking two vehicles was insurance: They wouldn't let me take two vehicles on a single credit card without their LDW. Thankfully I have a bunch of cards to choose from, and I didn't ask what they did with customers who weren't interested in the LDW period.

Maybe a quick call to a Manager at the location just prior to the wedding is in order?

Or, since you already know who the alternate drivers are, just put a ressie or two in their name?