You could all sign up for a membership in the Austrian Alpine Club (UK). Membership entitles you to a worldwide rescue and repatriation insurance (with some limitations) at no extra cost. As noted on the club’s website this cover is primarily for mountain rescue and is not intended to replace other travel insurance. Instead it complements travel insurance which often excludes cover for mountainerring and other „dangerous“ sports. Normal travel insurance should cover trip cancellation, emergency medical treatment and repatriation. The club’s annual membership fee is 41 GBP per person (31 GBP if you are under 25).
This was the option I picked for my trip to Mt. Kilimanjaro and the Alps in 2007. On the other hand, while SAR insurance is a necessary evil in the Swiss Alps where you can expect to be asked to shoulder a hefty bill for a helipcopter evacuation, it is a different situation in Africa. If you get hurt or fall ill on the mountain, there really isn’t much choice other than have your guides put you in their „ambulance“ (a one-wheeled stretcher) and rush you down the mountain!
„Hakuna matata“ and have fun in Africa!