Check out Jolinaiko Eco Tours. I'm planning on doing a trip with them in September. The owner and his wife are well known at the Dutch Embassy, if you want to get a reference. They have answered my emails promptly and professionally so far.
They advertise tours on their website for all three of the countries you want to visit, but three countries in two weeks is too ambitious, even with a four wheel drive. You'll spend all your time on the road and won't get to see much. I'm doing a two week tour of only Ghana, and it's not enough time to see everything I would like.
There isn't much to see in Togo. The infrastructure isn't as good as Ghana, and there are no real tourist facilities outside of Lome.