Weddingbee boards

Peanut patties or pralines? They sell them at El Fenix, which is a long-time Dallas staple (though not my personal fav)

The frozen margarita was invented in Dallas (at Mariano's)--if you want to include any boozy items, you could do a little bottle of tequila and/or mix, with the local history attached. Or a list of nearby places for a delicious frozen margarita (Gloria's! Mi Cocina! Cyclone Anaya's! Fuzzy's!)

I can't think of any good local snacks to include in the bags that you couldn't get elsewhere in Texas. Chips and salsa? Apparently, all I eat is tex mex. :)

If you're anywhere near SMU, Pokey O's has some good treats (cookies, flavored popcorn, puppy chow). There are quite a few good local bakeries, but those items couldn't be purchased/packaged in advance.

If I were your guest I'd appreciate the normal OOT bag type things--water, snacks, gum, etc, but with a really good list of local places to check out, maybe with a map/driving directions.