I am an Emerald Club member but still don't know how it works. If I book a midsize car, I can then just pick whatever is there?? I have a good rate for the midsize but wondering if it will be big enough for a family of 5 since it says it will fit 5 people but only 2 pieces of luggage. If I get stuck with the midsize will this be way too small for us (will have 5 pieces of luggage - two will be fairly small for my kids). Thank you!