Palm trees are tropical Angiosperms of the order Arecaceae, that have existed since the Cretaceous.
Coconut palm are one the most iconic representatives of this group due to the edible drupes (not a nut, but a special kind of fruit) they produce. First appearing in the Eocene, Coconut palms specialize in coastal regions and islands in the pacific. The large drupes are adapted to traveling at sea which allows them to colonize isolated islands. The trees themselves are well adapted to salt spray, sand and direct sunlight but cannot tolerate shading or cool temperatures (a cold snap can easily kill the tree).
Palms existed in Hell Creek, although Coconuts themselves are not known until the Eocene.
Ecology in Dinosystem
Palms prefer hot climates, especially around the coasts. The palms produces edible fruit (Coconuts) which are readily fed upon by dinosaurs. Saplings are browsed upon by Triceratops and Ankylosaurus. But adult trees are tall enough to avoid them.
Strategy in Dinosystem Survival
Palms are a source of edible fruit, although the fruit is not a nutritious as meat or eggs (although real coconuts are very fatty and thus calorie rich). Palms can also be harvested from for leaves & branches to make tools or use as fire fuel, or for resin to utilize the certain items like bandages. Palms can also be cut down with axes to obtain wood to use as fire fuel.