Any ideas on what to do?

I would be inclined to think that the best thing, no matter what you do, is spend time with him. Instead of going out to dinner, cook a nice meal for him. Home-cooking is definitely something he has missed, right? But spending time with him and making him feel at home is the only real answer.

Have you asked him what is the first thing he'd like to do once home? That could be a good indicator of what he'd be interested in doing.

Will he want to get outside on solid ground after being 'cooped up' on a ship? Perhaps a walk and picnic along a nature trail or forest somewhere outside the city would be nice. Or even the waterfront park.

Does he miss his friends and family? Maybe throw him a welcome home party and ask for those coming to bring something to contribute to the party.

If it's alone time you want with him then I'd still suggest a dinner of his favorite food at home, candles, soft music for easy conversation .... a relaxing atmosphere in general.

A lot would depend on his personality and what you feel would best suit his preferences. You know him better than anyone answering here.

PS: Something I've always wanted to do is have dinner in a hot air balloon. I don't know if that's available to you or not.

Why don't you go "sightseeing" like both of you are tourists. Look up some fun places to go and go there. I'm sure he is just eager to be on home soil. Whatever you decide to do, enjoy each other.