Hello Langin,
I haven't had too much experience with Skyauction but, I believe you can book more than one room at a time (just enter in appropriate no. under Quantity desired in the Bid on this Item section but if you must have three rooms, take out the check mark under "Yes, I will accept a lesser quantity"). I don't believe you can get any auctions at less than three days but you will most likely be able to book those three days either through the resort directly or through the no. that Skyauction supplies on the confirmation you get. Obviously, you won't get the same rate as your auction rate and you may have to change rooms (they'll tell you it will be up to the resort at the time).
Last year when I had booked through Skyauction we wanted to stay one more day. So I called Skyauction and they referred me to Extra Holidays (I think it's run by RCI) and it was no problem and, after checking with the resort, turned out we didn't have to change rooms.
I would send Skyauctions an email to confirm what you should do before you do any bidding. Everytime I've emailed them in the past, they have been quick to respond and helpful. Also the website pretty much contains all the info you need and you might find confirmation there.
Good luck and happy planning!
