I've taken the CDG-DLA flight before. Going down is fine, it's coming back that can be difficult as it is an overnight flight and it seems that most nights check in is bedlam at DLA.
Good that you got your visa in time. I didn't and had to bribe my way in.
I love the Deido neighborhood with its lively nightclubs. Hope you get to go. And try the anteater! It's a specialty of Douala and one of the best dishes I've ever eaten.