Manassas is just chock-full of mediocre-to-bad restaurants. There is, however, a pretty good Mexican place on Rt. 234(bus), Sudley Rd., just N. of where it intersects with Rt. 28, "El Rey Tolteca". I've been in there any number of times with no problem. There is also a "Cracker Barrel" just North of Manassas on the other side of I-66, but I understand they have a spotty reputation with OC'ers. Seems to me there's a "Famous Dave's" over there, too, but I can't remember for sure, I may be thinking of Centreville.
Since I don't have to be in Surry Co. after all on June 21, either that or June 22 would be best for me.