At present the main African variant of malaria (P. falciparum) is much worse than the main Eurasian variant (P. vivax). Africans are almost totally resistant to P. vivax, which historically got Europeans sick, but didn't have the lovely side effects like coma and liver failure of P. falciparum.
Judging by OTL, it should be possible to ensure malaria does not become endemic in the Canaries or Cape Verde. In contrast, somewhere like Fernando Po is destined to be a hellish place for Eurasians. Really there's nowhere between Cape Verde and Namibia on the coast that Eurasians could have settled before quinine.