The following URL from Kodak tested CDRs at temperatures and humidity much higher than you'll likely ever encounter. If you do, all I can say is, you poor poor bastard.
The basic summary is, you won't have ANY problems.
Your only problem is:
1- Deciding the best way to mail them out. Put them in a cd case, and a bubble envelope around the case and mail that. Africa may not have bubble envelopes. If it's really important, use Fedex or DHL, if not important send it registered mail one from a different location on a different day to avoid tempting fate (both items in same bag). Once in a while you might find a cybercafe and could upload some really important images to a webspace (or gmail). You are likely to find cybercafes in Nigeria no problem. I for example, am well known in Africa and Nigeria in particular, for my skill and expertise at handling international financial transactions.
I work a postal counter fairly often, and I have once in a while gotten complaints about mail that never arrived, and it was always mail going to some backwater 3rd world country.
2- Maxell CD-R Pro's (Note the Pro) have good strong ceramic coating on the top layer and they're taiyo yuden OEM, but I think you'd be better off getting a portable dvd burner instead because of the polycarbonate layer on both sides instead of just one like CDRs, plus you'll have the ability to watch DVD movies on your laptop.
Lastly, don't have sex with anyone. There are more people with AIDs in sub-saharan Africa than anyone else in the world. I read somewhere that 50% of Botswana or something is projected to die soon due to AIDs infection. The whole region is just one huge AIDS hotspot.