For Maun you do not need an instrument rating as all the flying is VFR so you can either do it before and then have to renew it after Maun or just do it after and save some cash. Not sure about Sefo but the other companies really don't care if you have it or not.
If Sefo ask for it and you want to work for the weirdest charter company in Maun then I guess before is your only option.