There's a couple nice places in LaGrange that might fit the bill. Marconi's is a demi-decent Italian restaurant that could certainly accomodate your party. Their food isn't out of this world, but it's pretty decent. Across the street is Via Bella which is another acceptable Italian restuarant.
There's also Cafe 36, which is a little more upscale, but I also like their food a lot better, too.
I don't know if this is out of your range, but there's also The Flame in Countryside, which is kind of an old-school joint that seems good for an 80th birthday party.
Marconi's
15 Calendar Court, LaGrange, IL
708-352-1621
Via Bella
75 South LaGrange Road, LaGrange, IL
708-482-0055
Cafe 36
22 Calendar Court, LaGrange, IL
708-354-5722
The Flame (Citysearch link) &
picture
803 Joliet Road, Countryside, IL
708-352-3442
-- Nora --
"Great food is like great sex. The more you have the more you want." ~Gael Greene