Thai Basil is one of the best Thai restaurants around. Yes, it is in a strip mall just off 50 past 28. Five minutes from Udvar-Hazy. Mikaku is an authentic Japanese restaurant at McLearen Square at the corner of Centreville Rd and McLearen. Five minutes from Udvar-Hazy.
Zeffereilli's in Herndon is an excellent Italian restaurant. It is on the other side of the Dulles Toll Road from Udvar-Hazy. It is more elegant than the others and is ten to fifteen minutes.
Otani's is a Japanese steak house where they cook the food and entertain. Lots of groups go there for birthdays.
None of these are chains.
http://thaibasilchantilly.com/about/
https://mikakurestaurant.com/
https://www.zeffirelliristorante.com/
http://myotani.com/
I also agree with a PP who mentioned Ford's Fish Shack, but it is a greater distance away.