The first thing I notice is that you are working together to improve the situation. That in itself is a good thing. Also, if your kids are 18 and 20, son't they spend a good deal of time away, working or going to school or studying? I had the idea that when my kids are that age, W and I will have plenty of time to ourselves.
If privacy is a big issue, how about a romantic evening or weekend away. Sounds like you won't need a babysitter.
