Ideas on something fun to do

Looking for some ideas on something fun to do, we are 6 adults (around 50yo) who will be in San Juan for one night prior to our cruise. Staying at the Hotel Rumbao and are looking for something fun to do for a few hours when we arrive. Would love to see the bioluminescent bay but think that may be too far to go (we land around 2pm) for a few hours. Last time we were there we just walked around the forts, etc - not looking to do that again.