I would highly recommend Rasika (Penn Quarter), followed by Coco Sala for dessert.

Both are pretty unique places.

I would avoid Georgetown. I know it's a popular destination but I think it's too touristy and crowded (and honestly there aren't THAT many great restaurants there, except Bourbon Steak).

I'd pick Proof, Fiola, Central, or Rasika. The last time I was at the Oval Room in the fall, the food was uneven and the atmosphere was kind of dull -- it was half-empty on a Friday night.

If the rooftop bar at the W is too much of a crowded scene for you, the bars at the Willard Hotel (the Round Robin) or the Hay Adams (Off the Record) are very "DC" but lower key, not crowded.

Yes, if they're not likely to get back to DC soon, you might as well walk past the White House at night. Especially if the weather's nice. You can do that easily from the Gallery Place area.

If you want something more upscale and formal, you could also do the Oval Room on Connecticut, which is about as close to the White House as you can get. Just step outside after dinner and you're at the corner of Lafayette Park.

PP mentioned the bar on the roof of the W hotel (above J&G Steakhouse). That could be the after-dinner drink destination, after your White House walk. It does get crowded, trendy, and expensive, but that's what comes along with the view and the good drinks.

^^ forgot to add there are parking garages on 6th St (Chinatown) and at 14th & U (U st)

If you think they associate DC with grand buildings and that sort of thing, I second the Portrait Gallery/ Gallery Place area. Poste at the Hotel Monaco is also housed in a beautiful old building and has good food and drinks. If they are up for a walk afterwards, just head west on G st for a few blocks and you get an up-close look at the White House & Treasury, too.
If your friends like ethnic cuisine and/ or nightlife, I'd suggest going for Ethiopian near U st followed by drinks at The Gibson, a speakeasy. I always take out-of-towners to Etete and they love it. The Gibson has very good cocktails but requires reservations.

OP here : thank you SO MUCH for suggestions! In response to one of the PP's - I do not really have a specific type of restaurant in mind in terms of upscale and cuisine - just a laid back atmosphere wehre we can enjoy each other, glass of wine and some food My friends are very chilled people so not demanding in this sense either. I just want this to be a nice memory of DC.

I recently went to Sax on 11th St (Downtown). The food is great and they have ongoing burlesque type shows (if you are not offended by that type of entertainment).

We love Filomena in Georgetown and out of town guests ALWAYS love it- especially the parts on the menu where it says what all the famous people ordered And there is a parking garage across the street!

J and G at the W hotel. Great view if the White House and you can walk in the park behind it afterwards.
I also second Gallery Place area lots to choose from and easy to get to.

The American Portrait Gallery, at Gallery Place, has a nice cafe and beautiful indoor courtyard. It's a nice place to meet up, see some pictures, and have that first glass of wine. Then you're surrounded by restaurants. Proof, Poste, Acadiana, Corduroy, Rasika, Fiola, Oyamel, .... Personally, I'd go with Proof. Almost right next door, and very good wine list. But options abound.

OP are you looking for a casual place, an upscale place, American cuisine or ethnic cuisine?

I like to bring out of town guests to Old Ebbitt Grill b/c you can't beat the location - the food was always just okay but recently I read a review (Tom Sietsema maybe?) that said there is a new chef and menu, both for the positive.

I like Bangkok Joes at the Georgetown waterfront. Certainly a nice area with a good view!

Friends from overseas are coming to DC during their US vacation , for two days. We want to meet them for dinner (no kids) one evening. I would like a place that also has nice surroundings, they have not been in DC before and most likely it will not be on their schedule in the future either.
That is why I thought G-town since that has a nice feel but I am open to downtown DC or other nice place. We will drive there so will need to find parking (which is why my Dh does not like the Gtown idea though I seem to recall parking garages there?), they will probably cab it.

Thank you for your recommendations!