Yes, DOLPHINS is a Scrabble word!

Letter values in Scrabble US: D 2, O 1, L 1, P 3, H 4, I 1, N 1, S 1.

Is it a valid word?

DOLPHINS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

large slender food and game fish widely distributed in warm seas (especially around Hawaii)
any of various small toothed whales with a beaklike snout; larger than porpoises