Yes, GENERATION is a Scrabble word!

Letter values in Scrabble US: G 2, E 1, N 1, E 1, R 1, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

all the people living at the same time or of approximately the same age
group of genetically related organisms constituting a single step in the line of descent
the normal time between successive generations
a stage of technological development or innovation
a coming into being
the production of heat or electricity
the act of producing offspring or multiplying by such production