Clothes: take more long/three quarter/zip off trousers and fewer shorts, likewise more long sleeved shirts and fewer t-shirts, for evening mozzie protection. Don't wear shorts on an early morning game drive (brr.) You'll need your fleece and a hat.
Light things like vests and underwear dried o.k. if you washed them quickly as soon as you arrived in the evening while the sun was still up, as did towels after use.
Namibian supermarkets sell effective mozzie protection and spray for your tent but take Deet with you and use it.
A sheet sleeping bag is useful in the desert as temperatures may not fall as far as you expect (in April, anyway.)
Our solar ipod charger was rubbish but we used a cigar-lighter one in the truck and it worked well. There are electric points by the tents at some, but not all, of the campsites.
O2 have no agreement with any Namibian mobile network even if you have arranged for roaming to be turned on.
Please do not rely on Namibian ATMs to provide you with all your holiday money. Even though we had all rung up our card providers beforehand, many of us found our (Maestro, especially) debit cards would only give 50-100 dollars per day (or nothing at all sometimes,) and our Mastercards would not work where there was no chip and pin facility. My own credit card was stopped completely when I tried to use it to obtain cash from an ATM, my Maestro card having only doled out 50 dollars. (Had a 'suspected card fraud' letter waiting for me when I got home.)
Do not expect to be able to pay for experiences/activities in Swakopmund by card, and check and double check the price just before you participate.
Malarone is the anti-malarial medication you need. You will have to get it on private prescription, but do not be tempted to make do with paludrine as it is ineffective.
We were lucky to have a good mix of ages on our tour, from 16 to us codgers in our 50's. We were worried that we would be in a middle-aged minority of two, but we weren't, and you shouldn't be concerned about this- everybody just wanted to be there and enjoyed it thoroughly. We took our 3 daughters whose ages ranged from 16 to 28 and they got on really well with everyone.
Namibian campsites are very well appointed and are in spectacular surroundings with bars, swimming pools and hot showers and an outside braai/boma area for sitting out. Exodus do camping the civilised way and you do not have to participate in putting your tent up, etc. This was such a blessing with the early starts needed. I watched people with other tour companies struggling to get their tents down at 4.30 a.m. in the pitch dark, and wearily putting their tents up in the evenings while we were just going off for a swim or a drink before dinner. (watched but did not offer to help!!)
If I can enjoy camping then anybody can, and you also get a very comfortable 2-day break in the lovely Swakop Lodge which has a wonderful restaurant and clean, well-appointed rooms.