Going on! It really depends on what you want to do.  

In regards to activities, I know you're specifically looking at Downtown but there's a ton to do all over the Metroplex. You're super close to Deep Ellum & Uptown (and the Design District), which are two of my favorite places in Dallas. Below I have included a list of restaurants, cocktail places, and activities (including music venues) that would be awesome for you both. I also included some spas incase your lovely lady needs some R&R... or you!  

Unfortunately, I am out of town this weekend but the Universe is a funny thing and I'm sure our paths will cross in the future. Have fun!

Restaurants & Lounges (again some of these are in Deep Ellum... I know that area well)
Five-Sixty  
The French Room
Nobu
Texas Spice
Papa's Bros.
Dean Fearing's
The Rustic
CDP Provisions in The Joule
Lark on the Park
The Woolworth
Kitchen LTO
Pecan Lodge
Filament
Brick and Bones

Activities
Reunion Tower Geo-Deck
One Arts Plaza
Sixth Floor Museum at Dealey Plaza
Dallas World Aquarium  
The Bomb Factory
The Church
Louie's Dueling Piano Bar
Truth & Alibi (speak easy)
Three Links
Lizard Lounge
Memphis (in Addison but it's a mix of current hits & throwbacks sung by a  live band... it's been fantastic every time I've gone).  

Spas
Bliss at the W
ESPA at The Joule
ZaSpa at the Hotel Zaza

If you should need more suggestions, feel free to reach out!