Good morning,
Moremi was closed until recently due to the rains flooding all the roads, it only reopened mid-April again. It is possible that the camps are fully booked with people that had to move their bookings due to the closure. The rain has stop but there is a bumper flood arriving from Angola soon, on top of already saturated delta, so you could expect the roads from South Gate via 1st and 2nd Bridge to Third Bridge being flooded again. I am not sure if Third Bridge is even accessible right now.
On Facebook, you can ask on the DriveBots or Moremi Sightings pages for updated information.
It does happen that people book the campsites and then have to cancel, Botswana does not do refunds so people just don't bother to cancel, they just don't turn up and then you can often get a spot, especially if you are a solo vehicle. For a group I would always try and book.
If Moremi is not accessible, look at the community campsites just south of South Gate, they are good alternatives. The road from Maun to Khwai has been challenging this year, with even the game drive vehixlxes getting stuck on the main transit road. The rain has mostly stopped now so conditions should be better.
Good luck and safe travels!
Kind regards
Lizette Swart
lizette@tracks4africa
co.za