You could make a tres leches cake for dessert... there's a recipe for that on the Pioneer Woman's blog. Looks easy to make, too.
I agree with Balrmerhon that it might be better to stick with things that are somewhat familiar to your guests already, like tacos, quesadillas, etc. You could maybe do some Mexican rice on the side. The flautas / taquitos would probably go over very well, though, if you want to give them something new along with the other stuff. Just shred some cooked chicken or beef with some Mexican spices and then roll in corn or flour tortillas and deep fry them. Serve them with salsa, guacamole, soured cream, queso or whatever dips you might be doing. Or just make some nachos!