If you have the money and you both have the time….
1) Tell him to clear his calendar for an evening and the following day. Refuse to explain why.
2) Book a nice room at a hotel somewhere within an hour’s drive. Or a little farther if options are better.
3) Pick him up, drive him there and [censored] his [censored] for hours and [censored] and [censored] and [censored]. The next day you can laze around the hotel and [censored] in the [censored]. If your [censored] isn’t [censored] you are not trying hard enough.
Anyway, the idea is be a little mysterious and take control, plan the whole thing and surprise him,