We did a 12 hour car trip when ds was 12 months old so a bit younger but one of the things we did was raid some friends toy boxes and borrowed some of the toys that they had for him to play with on the trip. Things that are easy to play with while sitting but that you know that your little one will like playing with. Gave the novelty factor as they weren't his toys but saved us from having to buy lots of new toys for the trip.