The adventure is now / Jess Redman.

Enhanced descriptions from Syndetics:

A fun-filled, action-packed middle grade novel about a boy who learns about protecting the environment, finding real friends, and living in the now while spending the summer on a remote island.

Sometimes it's hard to be Milton P. Greene. He says all the wrong things, his family is falling apart, and everyone at school avoids him because of the very embarrassing Bird Brain Incident. But when Milton plays his video game Isle of Wild , he becomes someone else--Sea Hawk, the brave and brilliant naturalist explorer who conquers danger at every turn.
Then Milton's parents ship him off to the remote Lone Island for the summer, where his uncle Evan is an environmentalist researcher. The island is chock-full of spectaculous species, and Milton realizes this is his chance to become the brave and brilliant naturalist he's always wanted to be--and even meet some fellow explorers!

But as it turns out, the future of the Lone Island is in some pretty serious peril, and the only thing that can save it is a field guide full of cryptic clues. If Milton and his unexpected new friends are going to protect the island, they'll have to trust each other, discover new truths, and embark on a wild and wondrous adventure all their own.

The Adventure is Now is a dazzling, fun-filled story from Jess Redman.