My son is a climber too, it's crazy how high kids can get. But climbing trees are a lot different from climbing household items. Even if the branches are small enough and within reach, he'd still have to have the coordination and balance for climbing uneven branches, and that's ignoring the things like how damp leaves or branches would make it even more challenging. I'm not saying he couldn't have climbed a tree, but find it so unlikely that I don't consider it worth any serious thoughts.
Don't think there are any marshy areas. The bigger problem would be the rains causes ditches and other low areas to flood. Some areas that were bone dry the day before can turn into a small pond/late over night. However, they have stated that they have checked any ponds/flooded areas and it was clear.