Park at the Blu Emu carpark (Ross Smith Ave, Mascot) which is immediately left after the BP service station or just turn at the service station if fear of missing it if you want cheaper parking and catch the courtesy bus to the airport. Alternatively, park at P2 and pay more money. Walk the 8 minutes to the terminal. For your first time, plan to get to Sydney airport at least 3 hours before your flight leaves. You will need the extra hour for traffic delays or your wrong turns. If you catch a train, to get off at the airport, it costs heaps more, though it is an easy experience. Just be mindful of only taking enough bags that you can handle to carry if catching the train or courtesy bus, especially if you have younger children. If you have younger children, go straight to P2 parking.