There's no good beach in Galle at all. Instead you have miles of huge rocks piled up as a breakwater.
If you want tosmewhere with plenty of alternative eating places , in that area, then you'd have to look at Hikkaduwa, Unawatuna or , to a lesser extent, Mirissa.
Neither of these has the choice of hotel that you'll find in the Bentota area but there are some good places there.
Coral Gardens is the best of the hotels on the coral reef beach in Hikkaduwa.
For trips out locally, there's the moonstone mines just outside Hikkaduwa. The mask museum at Ambalangoda just a lttle way north. Turtle hatchery at Kosgoda., Galle Fort, etc..
For longer trips with a car and driver it's possible to visit the Sinharaja rain forest reserve or Udawalawe National Park to see the wild elephants.
Plenty of shops, bars and restaurants, in Hikkaduwa.
For longer trips, such as the hill country, or anywhere in the cultural trioangle you'd need to stay out overnight in an inland hotel of guest house.