First of all, junction 30 of the M6 is the junction with the M61, so you can't get off the motorway there. Anyway....
I know of a couple of places slightly further north. There is the Phantom Winger just off junction 32. You have to be careful because you initially follow signs for M55 Blackpool then (and you have to be REALLY careful here) take the M6 to Preston and Garstang, NOT the M55. Turn left at the roundabout and immediately left again, at the roundabout at the bottom go straight across in the Phantom Winger car park.
http://www.eatandplay.co.uk/info.asp?RID=223
Or, if you are travelling northbound you can exit at 31A, follow signs for Longridge, and after about 3 miles, after travelling through Grimsargh you come to Francos restaurant, which is really popular with families.
http://maps.google.co.uk/maps?hl=en&um=1&ie=UT F-8&q=francos+grimsargh&fb=1&split=1&gl=uk&vie w=text&latlng=3940014556023423324