There are plenty of intervalometer scripts around here. Just
search for "timelapse script" or "Intervalometer". You can basically use any of them, but i suggest you try some out and check which one is easiest to set up or to use..
You can load scripts at any time after booting chdk over the scripting submenu, thats where you can change script options too.
I really suggest you play around with chdk a little, maybe to a test ride with your bike + cam to see if everything works as expected..
A little offtopic:
From cairo to cape town - isnt that something like 8000 km? How long do you think will it take to do that trip? And what i'm really curious about: How to you charge your batteries? With dynamos on your bike? (I know they have electricity in afrika too.. But still, those ixus li-ion battery probably only last 3-4 hours)
