I find a small towel folded over the lens and body works just fine in light rain. Two or three folds with a larger towel will get you through a heavy rain for a time. The towel will get heavy as it gets wetter, so a tripod will help if practical.
When I photograph high school golf I bring a 70-200 with an R5. The only two shots in golf that really have impact for me are close-up follow throughs on drive swings and coming out of bunkers with sand flying. Of course Augusta is a beautiful place and since your photographing celebrity pros, you’ll need wide angle to capture the full gamut of the event. So I think your selection of the 24-105 and 100-400 is perfect. I jealous. Have fun!