We're staying in Dubrovnik.
Fair warning- it's as expensive as hell. Our hotel is 300 euros/night
There are lots of cheaper options but they're further away from the old town. We wanted 4-star or better and close to the old town but also with a beach (so I can walk to the old town bars while Irina's sitting on the beach
)... narrowed down our options. Plus it's high season.
But a decent place anywhere for less than 200 euros/night is hard to find unless you rent an apartment, which might be a good option for longer stays.
Apparently the beaches around Dubrovnik are all pebble beaches, not sand. Not sure if that makes a difference to you.
From what I read, there are a lot of cultural events (concerts, performances, etc) in the summer. Our more traditional nightlife is supposed to be OK but not spectacular, although restaurants and early evening bar-hopping are supposed to be quite good.