The orchids (probably) will slowly grow enough roots to encircle the bamboo, this "attaching" themselves to this surface. I don't think bromeliads ever would. Another (possible) problem is the density of the bamboo. It holds no moisture and your plants would really dry out quickly mounted on them. Find some old, beaten up wood somewhere, anything will probably work so long as it is not treated, mount your plants on this and then hang it from the large tree's limbs. Your cat, or most anything else, won't bother them. However, and this is a true story, birds might nest in the large plants, particularly large orchids in 10-12" baskets. Two years ago I had a pair of mourning doves nest in one of my basket-orchids and raised three young ones. I just left them alone and by mid-summer, the young were old enough to fly and they all left the nest, never to return again (at least not so far).
