sally.
We have been to The Gambia many many times and feel we know whats what and where. My advice is to only book a hotel that has at least 4 stars. Even then you have to be careful. There are no doubt several that can be recommended and I do so for the Hotel Atlantic which is part of the Corinthian International chain. Fantastic.
Do NOT risk a bad experience in this lovely Country by one of the many inadequate places to stay.
Check out the Gambia Experience. I reckon they are the only way to go.