Like Bonty said, you can drive in to Wilbinga. It is a sand track from Wilbinga Grove roadside parking area off Wanneroo Road.
But from there you are only allowed up the beach as far as 500m before the Moore River and can't cross the river mouth from the beach. Have to go back out and around to go further north. You can drive in again at Seabird.
Or go up to Lancelin and have a play in the dunes and follow the beach tracks up to Wedge Island.
Or drive all the way up to Wedge and head back along the beach.
Really there are hundreds of kilometers of beach and tracks north of Perth, how far you want to go.