If you are going for a relaxing holiday it will be fine but if you want clubbing then it is not the place for you.
Cala Galdana is in the Southern end of the island and if it is a clear day you can see Majorca wel the Northern tip anyway. There is not a lot to do there and most of the entertainment is in the hotels of which there are three main ones. The Cala Galdana, Audaux and Sol Gavilanes they all have entertainment but of them I would say the Cala Galdana has the best. There is a small marina and there are a few resataurants sprinkled about but as I said it is more a place to go and relax and get ready for the rigours of winter. We were there in June this year and it was quite busy with holidaymakers ranging from very young to those who are in the senior years. I enjoyed the week we were there because of the pace everyone seemed to adopt. Perhaps you could hire a car, as we did, for three days to let you see a bit more of the island.
One thing if you do stay in Cala Galdana you will need to go to Ferreries or El Mercadal for you cigarettes as they are the only places close by that have the Tabac shops.
not sure what the weather will be like at this time of year but is was fine in June have a nice one anyway.