Joe, despite the obvious bias in favor of doubles on this forum, I think there is good reason to consider something other than an automatic. I began shooting in Argentina in the late 1980s. I started with a Remington 11-87 with an Ithaca 37 in reserve, both 12 ga. My experience was that the gas operated automatic became a one-shooter unless I spent lunches stripping and cleaning it every day, and the light Pump-gun kicked too much to enjoy shooting on a hot-barrel dove expedition.
Next trip and ever since I've carried a Citori 12ga o/u without a backup. The heavier Browning has been a pleasure to shoot and thoroughly dependable. A Citori 20 with 28" barrels would probably be an even better choice, and still plenty of gun for everything I've shot in SA.
The Benelli style recoil operated autos wouldn't foul like the gas jobs. However, I think the recoil would be a problem like the light pump I used.
I hope you'll try something besides just the dove only trip. Three or four days of South American style dove shooting is just TOO much shooting. The mixed bag trips including a sample of eared dove, pigeon over decoys, pediz over pointing dogs, and duck species you've never seen before is a more enjoyable trip and when you discount the $10 a box shell bill, about the same price. Just my opinion...Geo
