I also did a lot of beach time whilt I was there. First was the family pilgrimage to Bojo Beach in Accra which is an absolutely beautiful white sand beach - you certainly don't get beaches like that in England! They also do the best chicken kebabs.
If you're looking for somewhere outside Accra then I highly recommend the Coconut Grove Beach Resort in Elmina. We ended up going there as an impromptu thing for two nights as a big family group. I don't think anyone regrets it as it was an incredibly relaxing experience. I think I walked the length of the beach 4 times whilst I was there. Everything was really tidy, the rooms were nicely air-conditioned and the food was very tasty. Service may have been slow at times, but then again I don't think they were used to such a large group of people all at once!
We also went to visit Elmina Castle whilst we were there. It was a very different experience to anything I've done before. It was mind-boggling that where we were standing used to be 100s of slaves shackled together. Apart from that, it was a good experience and I'm glad I went.