I don't know of a really good way to handle it that is fair for everyone...
I like the first come, first serve method - but how manageable will that be if people just send a bunch of payments to you, especially those for the same plot? For example, let's say there is a particular plot for 1,500 and 5 people pay you the money right around 6pm CST. Take all the plots into consideration and it will be a massive influx of payments to you. Maybe I'm overestimating the interest in the plots --- especially particular ones, I don't know.
The bidding war method, however, will be even more crazy and the chat will be filled with back and forth discussion, not to mention the plots being driven up in price, which will alienate those who have been saving up for a stated plot price but don't have enough money to bid any higher.
I know you will figure something out - I just wanted to put my thoughts out there. I personally just really want the K18 Plot for $4,000.
Good luck to you and to everyone!