We received the last responses (via phone) from guests yesterday and we are now 100% done with figuring out seating. Because I wanted to be able to physically move people and tables around, I did a posterboard chart with paper plates and colored post-its (which several of you suggested).
When I stopped by Walmart to pick up the posterboard and post-its, FI kept insisting that I was being silly and that we should just use one of his drafting programs to do it... but once we got going and he saw how easy (and colorful) it was, he caved and said that it was definitely easier and more fun, haha.
So thank you for all of the suggestions and here's a picture of our not-so-difficult-to-do seating arrangement poster (which has since been converted into an excel spreadsheet)...
