Chansey is a Normal-type Pokémon, so its weakness would be the Fighting-type. However, it is completely immune to Ghost attacks. But it doubt Dragonite would have either of those.

[Already, Esuna is coming back, trilling excitedly. Cecil listens to her cries for a few minutes.]

It appears a Chansey is snacking on berries further south. Alone, with no hiding places or ledges around. A surprise attack would be impossible.