T.F.
I don't know your budget....
Hotel ZaZa downtown is really nice and has a spa
Crescent Hotel Downtown, good spa
The W
Alolphus, DIning there is awesome...very $$$ and jacket required
Gaylord Hotel in Grapevine
The above hotels are very nice, some quite pricey but they have couples packages as well.
Start having date night EVERY WEEK. We made a vow to never miss date night unless someone was sick. You don't have to spend a ton of $$ on date night. You might just want to enjoy a long walk with no kiddos.
Best wishes!!