Can anyone tell me if we'll be able to use the curbside check in at LAS to check in before we return the rental car? So basically we're not having to lug the luggage back on the bus from the car rental centre? Cheers! 
Yes you can but the only issue you will face is where to park the car while you check in. It's a drop off only area so you can't park up and leave the car while everyone all goes to the check in desk. There is a longer waiting area at the end of the drop off zone but it's restricted to limos and meet/greet vehicles. We've always just taken the hire car back first and lugged the bags.
An alternative is to drop off one of your party with the luggage at check in while you then drop off the car, then all check in when you get back.
