I bought a 10mnth old gelding in 2007 that hadnt travelled before.
It took us 2 and a half hours to get him loaded as he just wasnt sure about this big box thing
Eventually after a lot of patience he loaded and he never moved the whole journey 2 and a half hours home.
As long as you leave plenty of time before the journey incase they dont load. Can you try and get them used to a trailer/lorry before hand??