If the plants are still dormant, you have done the right things and keep them in relatively cooler and darker place until the weather allows to plant it outside in a week or two. The roots have to be covered in moist peat.
If the trees have broken dormancy, then plant them in pots using preferably soil from the garden (or commercial garden soil) and keep the pots in lighted area. This way you can keep the potted plants for much loner and plant them anytime at you convenience. It will be preferable to avoid breaking the rootball then so the tender roots are not damage putting back the progress.

Thank you!