If all else fails, hot decaf tea is fine; so is warm milk.
I learned something interesting about black tea the other day.
If you steep it a short time, i.e. a couple of minutes, the caffiene is prominent.
After a couple of minutes, the tannins, which are relaxing, start to come out.
So, if you steep your tea let's say 5 minutes, the caffiene becomes subordinate to the tannins, and you have a relaxing cup.
I've been making darjeeling tea in the evenings, steeping it 5 minutes, and it's quite relaxing.