I can understand your wanting to place those trees in a much better environment. Most gardeners agree that the best time to transplant a Maple Tree is in the mid Fall to early Spring months. I did locate a link that will give practical advice on the actual transplanting of the trees.
to view the link. Keep in mind that an expert will be
responding within the next two business days if not sooner and will likely offer you more information and
instruction. I hope this information will be helpful and have a nice day.