A big secret: use the (free) car park on the corner of Thanet Court and Wantirna Road. Eastland is a five minute walk from there.
The best place to park is at Eastland Shopping Centre. I always manage to find a car space (might be the time I'm going as well)??
May become little more difficult with new developments
Like what Robert has said, apart from the holiday season there is usually plenty of places to park at Eastland. Due to the amount of entrances to the complex you will be sure to find one close to the entrance.
I find in my experience that Eastland is pretty easy to park. If you struggle for car spaces always try near the Cinema as you are bound to find a car space. I hope this helps. Robert Cincotta