Yes, AESTIVATION is a Scrabble word!

Letter values in Scrabble US: A 1, E 1, S 1, T 1, I 1, V 4, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

(zoology) cessation or slowing of activity during the summer; especially slowing of metabolism in some animals during a hot or dry period
(botany) the arrangement of sepals and petals in a flower bud before it opens