Moving plants into containers now, for a few weeks?

[Anonymous]

I have a yard with many mature but now-crowded plantings (due to the previous homeowners) and after a couple of years getting my feet wet at gardening, I'm ready to divide plants, etc., and make room for ones that are better suited (esp since some are in shade that should be in sun, and vice versa). I have some friends who will want these plants but aren't able to retrieve/plant them for a few weeks (late April or early May), and meanwhile I want/need to get going on reworking my perennial beds. So one solution we came up with is my putting things into pots for a few weeks.
I was wondering if it would work for these plants--which include:
-hostas [to be divided]
-astilbe
-ligularia dentata
-hydrangeas (the smooth/native kind)
-Hakone grass

If so, would I need to use potting soil in these containers, even if the plants were already planted in the soil? If they do need 'potting soil', could I simply mix in perlite/vermiculite to my own soil?
Does the fact that it's not yet 'last frost' have any repercussions on whether this is a risky strategy for late March/early April?
What, if any, fertilizer would be best to use after putting them into the container (and/or having divided them first, like the hostas)? Unfortunately my compost isn't ready now; I've read that MiracleGro can cause the wrong kind of growth for plants at different points.

[Anonymous]

Your plan should work; it's what native plant sellers do too. I wouldn't bother with fertilizer, you risk burning the roots. The soil it is in should be fine.