This is in fact all theoretical, right now. I'm not even sure what the park would even go for. The problem I see with the second 18 is a lack of play. We have 2 standard 18 hole Par 54 courses within 15 minutes of us and 5 more within 30 minutes. When anyone comes here they want to play the long course, no matter their skill level. For tournaments I was thinking 27 holes a day. 5-10 minute breaks at the end of each 9. The Par would be 108.
My initial thought was 2x18 -- that's the layout of my "home course" at Armco Park. Blue course is longer, white course is shorter, both are pretty tight and technical. I like having the option, especially since my DG time is rather limited.
Given what you've just said, though, I'm thinking that it might be better to go 27. I would try to make it so that people who want to play 18 can do it easily (if you can lay it out so that all three nines end close to the parking lot that would really be sweet).