I havent been to Sandibe camp, but I have been to other camps in the Okavango.
Think layers and malaria proof! The wet season is still quite steamy, so layer your clothing for easy take-on and off. Also, if you can manage to get clothing with DEET in it (I cant remember what they're called, but should be available at good travel equipment shops) - highly recommend it.
I wore a thick "hoodie" jacket at night time around the fire because the temps fell quickly.
You might also like to consider thermals for sleeping in.
Enjoy, the Okavango is such a beautiful place. I cant wait to return one day. almost 9 years ago