Answer: Whether the new plants are seedlings or suckers, they're still crape myrtles and you should be able to dig and replant them in your garden next spring. Seedlings will have their own root systems; suckers will also have root systems but will be attached to the original root from the mother tree. You should stil be able to cut through the root on either side of each sapling and preserve each new plant without damaging the overall health of the mother tree. Losing one suckering root won't hurt the tree.
Best wishes with your free plants!
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