If you stay at the Castle you are ski in - ski out and very near to various ski schools and ski hire places. I guarantee you it will all be very easy and convenient. You might also consider Evridika Hills (again ski in/out) that is another really nice place to stay right next door to the castle. You can find it on booking.com I think.
Wherever you decide to go I hope you have a great time; it's a wonderful resort.
If you prebook with any of the main tour operators it will be ski centre 2 at Malina depot you are booked with. Not all that convenient if you are staying anywhere near the mid station although most places should provide a shuttle bus.