If the person who is watching your children for the night could watch the kiddos as their house, you could plan a great "date night" at home for much less than going out.
- order Chinese take out (usually under $20 for 2 people)
- make his favorite dinner (great pasta dishes or even steaks can be done cheaply)
- nice bottle of wine or favorite beer
- watch his favorite movie (even if you've watched it 100 times and still don't think it's funny...)
This is NOT a criticism (seems like people are a little touchy on this site today), but if he's stressed about finances and doesn't want to spend money to go out to dinner, then you can make him feel special by respecting that and staying in for the night!