Move over winter while they're dormant, and bear in mind that, even though its only been 3 years,the root spread is likely to be extensive - keep a good rootball at the base and extract the longer roots intact, make sure the new planting area is shaped to fit all the very long roots, don't bend them or cramp them into a new hole.

Thanks Bamboo

I find it best to dig and prepare the new holes before digging up the trees. Dig it larger than you imagine that you will need and mix in compost and bonemeal.This way if you are running short of time there is already a hole to put the now bare-rooted tree into. Also, don't forget to stake and water the re-sited trees all of next spring/summer while they re-establish themselves.

Thanks Volunteer