In most countries anywhere....NO.
In most countries third world or not, there's NO right to own arms, nor any right to protect and defend yourself.
The only people allowed arms are the ruling group and their small circle of supporters.
The certainly are NOT going to allow some group of foreign aid workers to have guns.
The local governments don't like anyone having guns but them.
Most African governments are actually tribal in nature, often the people needing aid are from another tribe, and they really don't want them helped to start with.
SOME aid looks good in the press and the UN, but EFFECTIVE aid, protected by guns is NOT desired.
It's not unusual for the ruling tribe to be closely connected with any "bad guys" in the area, and they flat don't want anyone being able to resist the gangs.
Finally, no country, especially third world wants to admit that they're not in control of their own country, to the extent that foreigners have to arm themselves.
Bottom line: If you're going overseas to provide aid, be prepared to face whatever comes along as an unarmed victim.
Arm yourself, and even if you can get them into the country, you will be quickly expelled if you're lucky, or tossed into a hell-hole jail if you're not.