Pastida is a pretty and peaceful resort that still feels like a village and generally offers excellent standard accommodation. It's just inland of the west coast resort of Kremasti so your airport transfer will be very short but you're not directly on the flightpath.
There's no beach in Pastida as it's a 5 minute drive inland from the coast though i believe there are buses or a taxi will cost you very little to the nearest beach (Kremasti). If i were you though i'd hire a car as Pastida is just off the road that connects the east and west coast - a 10/15 minute drive and you're in Faliraki. Kremasti beach is rocky and shelves quite steeply into the sea though there's always a pleasant breeze, the east coast beaches tend to be sandier and shelve more gently so i'd imagine they'd be better with young children.