I think a guitar is the best bet.
You can play and sing with it, which can not be done with blow instruments, and someone else can join in the singing.
Ukulele sounds OK too, but I never used one - except in a store the other day, and I kind of liked it. And it is small too.
Keep in mind that plain harmonicas or "harps" can not readily play all notes, unless bending notes, which takes time to learn, plus they are somewhat fixed as to a key or scale they are tuned too. Harmonicas are great, though. I also play them, but they do amount to cost. I sometimes play harmonica together with guitar with a neck brace. So maybe don't limit to just one choice - except for starting - and for starting, I think the guitar is better, and I mean an accoustic one, which needs no gadgets and is more portable.
Harps may be cheaper than a guitar, but they do go bad, then you may have to buy another one, since repairing is not that easy.
I think it should be more to what you like more than hoping to please others, which is inherent if you like and dedicate yourself to it. But this is just my thought, and surely not a total truth.