I'll go out on a limb and assume we're talking about Michigan. ;) The quickest, most direct route is via Lansing. Starting in Jackson, you can either go around Lansing by taking US-127 north to I-96 westbound, or you can go through Lansing by taking US-127 north to I-69 south to I-96 west. (The latter route sounds crazy but it's almost as short as the "going around Lansing" route; look on a map and you'll see why.) Both of the Lansing suggestions below use the latter route, i.e. you have to take US-127 north *past* the I-96 interchange and keep going; then after lunch you can continue on US-127 north to I-69 south to I-96 west to Grand Rapids.
If you take US-127 north past I-96 to the Lake Lansing Road exit heading westbound, you'll see the Eastwood Town Centre mall on your right. There, you'll find Mitchell's Fish Market, an excellent seafood restaurant, open for lunch seven days a week. www.mitchellsfishmarket.com
The previous exit from US-127 is for MI-43. If you take that eastbound, you'll head right into East Lansing. Beggar's Banquet is an interesting place. I went there many years ago and at the time it was excellent, but I don't know how good it is these days. But it's definitely open for lunch. www.beggarsbanquet.com
Alternatively, you can go all the way to Grand Rapids, where there are a lot of excellent places. My favorites are (1) Leo's, in downtown GR, open for lunch Mon-Fri and specializing in seafood, www.leosrestaurant.com (2) Bistro Bella Vita, also in downtown GR, also open for lunch Mon-Fri, and specializing in natural and Italian/Mediterranean food, www.bistrobellavita.com and (3) Rose's on Reeds Lake, southeast of downtown GR, open for lunch 7 days with bistro food on a beautiful lakeside setting, www.thegilmorecollection.com/Rose%27s...