Any type? How much are you looking to spend? Is this going to be a more casual or formal get together?
Seeing Frankfort (my hometown) on LTH first thing Saturday morning is quite the shocker! I didn't think anybody ventured that far South. You may find that the majority of establishments relinquish flavor and authenticity for consistency and familiarity; one of the many reasons I got out of Frankfort as fast as my fat little legs would carry me was that the state of chow in that town is dominated by a few semi-local "kingpins" who've abandoned all pretense of anything beyond hyper-predictability. In the interests of assistance however, here are a few relatively new places which you might find serviceable for your needs:
Irish-American pub food can be found at Galway Arms on Rt. 45/La Grange near Lincoln-Way East, behind the Buffalo Wild Wings. From what I can remember of my last trip a few months back, the warm wood-and-stone dining room circles a large faux-fireplace, with live music on the weekends. I had a burger, which was decently prepared and wasn't oversalted or over-Mrs. Dash'd like other places in town. My dad had the shepherd's pie, which he said he liked, but given that he is also very fond of my mom's cooking, I'm not sure how much I trust him.
If your friends are from Frankfort, they're likely familiar with Rising Sun, as it is far and away the best Chinese (even though it's really Cantonese, don't tell the neighbors) in town. If they aren't familiar, it might be a slam dunk. The menu is pretty vast and accomodates everything between not-at-all-adventurous to the weekend-warrior palates. Dishes are made spicy on request, really spicy and not just "tarnations i knocked over the pepper into the wok" spicy. This is one of my favorite places to eat when I have to go home, but once (in years of eating there, so I don't hold it against them) I did come away with a dizzying MSG headache, so be warned. The location in Frankfort is primarily takeout, but the one in Mokena (about 5-10 minutes north on Rt. 45/La Grange, between the Clark station and Wendy's; if you hit 191st you went too far) has a decently sized dining room.
If Rosebud-style Italian is more their speed, you might try Villa Rosa in downtown Frankfort (in the shadow of the town's only landmark, the Grainery!). This was my reliable go-to for pepper and egg sandwiches, since nobody else in town offered them outside of Lent. Not sure what else I can add outside of Rosebud-style, it is early in the morning and I am going to find food since now I have gone and gotten all hungry, attention span be damned.