Bummer! My husband never wants to do dancing classes either!
We've been married 16-1/2 years and 11-14 years of marriage was a tough period for us. Now things are smoother but it takes some effort...and it takes some time to remember to relax!
One thing my brother and sister-in-law do, that I think is awesome, is they have a surprise outing that each one of them plans sometime in the year. Whoever is planning the next one, reserves the weekend with the other to make sure there is not a time conflict, and then the planner makes all of the arrangements. It may be as simple as a camping trip with some hiking, it might be a tour of some obscure place with a nice dinner somewhere, or it might be a B&B trip planned for an entire weekend.They trade off making the plans, so they don't get into a rut of one person always doing all of the work. And it has become a long-standing adventure of surprises for them as a couple.
My husband and I have a funny little tradition that we started on our honeymoon. We have a running rummy game that is one continuous game that we've played for 16+ years. Our totals are in the 1000s. So, every once in a while, we pull out the "book" with our tallies and play a few more games. It's funny how a rummy game can be a little romantic interlude, but it actually is for us. It's just kind of a reminder of keeping it simple, even if it gets late.
Another thing we sometimes used to do, when our son was younger, was to have some special time with him. Then after he went to bed, we would set up some candles and just hang out together in the living room. In the beginning, we would just sit there because we'd forgotten how to talk with each other. But don't force it. Now, we've cultivated the candle thing so that we can relax and catch up with each other. Or a nice quiet sit by the fireplace creates the same relaxed setting.
We've never really had the option of relatives taking care of our son, to give us a night off, so it comes down to working with friends or babysitters. If sitters get too expensive, then see if you can arrange things with friends, parsing your kids to different homes or to one family that enjoys a crowd...their own kids, plus yours. (Just make sure you feel comfortable that your kids are safe, whatever route you take.)
As your kids get older, you may find that they begin to go to overnights at friends' homes. If you begin cultivating periodic overnights at your house now, you may find that you can coordinate with friends' families so that you can have an occasional night to yourselves, whether it is at home or on the town. (The old "I'll scratch your back if you scratch mine" kind of thing.) In the last year or two, we've found ourselves enjoying several quiet nights at home to ourselves. What a novel thing!
I can't stress how important it is to remember that you are a couple as well as a family with kids. One is essential for the other to work, either direction.
Best of luck and enjoy!