Definitely need more details, but I used to take my Mom out on the Saturday night before Mother's Day. We dined without crowds and quite leisurely.
Most restaurants on the actual day are crowded, over=priced, fixed menus, etc. That usually equates to bad service, lots of screaming little ones, etc.
I hope that I don't come off sounding snarkey, but since your Mom is retired I am assuming that she would probably like a more subtle, laid back dinner, then the madness of the Mother's Day Sunday.
The two of you could share a sweet, cozy breakfast, brunch, lunch (whatever) at home on Sunday--perhaps using leftovers from the night before.
Just a suggestion. IN any event, very Happy Mother's Day to the two of you. FoiGras
What a nice opportunity to finally be able to celebrate with your Mom. It would be good to know if you have a price range and if your Mom likes any type of food in particular. Also are you looking for dinner or brunch/lunch recs?
The more details you give us, the more we can help you.
One thing I know for sure, I highly recommend making reservations ASAP since this is one of the busiest restaurant days of the year.
Mother's Day is another one of those special occasion days that tax restaurants to their limits and often ends up looking like amateur day. After you have provided more info to help us narrow your choices as another poster has suggested, you should look at past postings that are specific either to Mother's Day, New Year's or Valentine's Day to see how the restaurants on your short list have handled the pressure on those days. Places that rarely fill every table are unlikely to be staffed to handle the pressure. This includes top dollar joints. I recall a scathing review by one poster about the difference in treatment at a high end steak house on a holiday evening vs his prior, non-holiday experiences.
That being said, we took a spur of the moment trip to Huong Viet on Mother's Day last year, arrived at 11 and had a pretty darned nice Vietnamese meal. Nothing special for Mother's Day, just their consistently excellent cooking at a restaurant that routinely fills every table for weekend lunches. By noon the line waiting forlornly for tables was out the door.
Huong Viet Restaurant
6785 Wilson Blvd, Falls Church, VA 22044
It's good that you can treat your mom this year, but you realize that there are thousands of places that could qualify in the large area you've mentioned? A little more info, such as type of food and how much you want to spend per person, as well as preferred location, will get you better suggestions.