yes, take the visa card and maybe a visa debit card (cirrus). forget about mastercard, if you travel west africa. no travellers checks. euros in west africa, dollars only for ghana and nigeria (the rate is slightly better than the euro rate)
be careful in some places, eg. Togo, it can happen that the atm does not give you money but the bank takes it from your card.
euros are best in west africa. east africa you can manage with both mastercard and visa easy, but better to have debit cards.