The current weather you describe is not particularly harsh. Mulch after planting to protect roots from any significant cold or drought that may occur later. And choose planting sites where tops will be shaded during severe weather, roots not subjected to much heating of the soil by direct sunshine.

There won't be any transplant shock if you just pop the plants out of the pots and set them in the planting holes. Due to their density and brittleness it really isn't feasible to pull open the roots of container grown heath family plants at planting time. If it does appear some correction may be called for then maybe trying the method of taking a butcher knife (or other suitable weapon) and shaving the outside of the balls so that they become square in outline would be useful. This serves to address circling of the outside of the root system but of course does nothing about any internal defects that may be present.

Initiation of new root production by cold climate adapted woody plants occurs in spring, when the tops start to grow. There will be little, if any root growth on the particular examples you have been looking at now, if their tops aren't growing yet. The general annual pattern is initiation of new roots in spring, some root growth in summer, significant elongation of existing roots in fall, little or no root growth in winter - when plants in this group effectively hibernate.

I think the issue here is likely to be how wet the soil is rather than the temperature.

If you "just pop the plants out of the pots and set them into the planting holes" you're pretty much guaranteeing that the roots will not extend into the native soil. You will do no harm to rhododendron root balls by forcefully exposing the root ends or cutting the roots. You can use a stream of water from a hose, a wire tined cultivator, or a knife to do this. You do need to exercise reasonable care that you don't accidentally sever the whole rootball from the main stem, but this process of exposing the roots is important in establishing a rhododendron. The Rarefind Nursery catalog and website has good illustrated examples of this process. In some cases where the native soil is extremely (and unusually) rich in airspace and organic matter or has been made this way in a large area, just popping into the hole may work. In most cases, though, the plant will languish, sometimes for years because the roots never ventured out of the peat-based planting mix. This, in turn, becomes harder and harder to wet and loses essential air holding capacity as it breaks down.

As for planting, probably this weekend will not harm the plants, but why rush? This is a historically miserable non-spring in the East. Removing the two rhododendrons from the protection of a hoop house to an environment of harsh winds, sleet, snow, drenching rain, would be a very sudden and stressful change. Until the weather settles, the soil dries out to some degree and night time lows remain above freezing, the plants are better off where they are. Transplant shock is really not an issue in pot grown rhododendrons. In fact, unless we are talking about bareroot stock or attempts to establish trees in droughty high summer, "transplant shock" is usually trotted out as an explanation when the speaker has no idea what ails a particular plant.

Another good reason to wait that I should have included above. In my experience, Cherry Cheesecake is very prone to aborting its flower buds if they have started to swell at all and are then hit with sub freezing or even close to freezing temperatures. If your CC has a lot of buds, wait until the danger of serious cold is over before planting out. This may mean well into May this year. You can certainly bring it home, but it would probably be best to keep it in its pot until after your last frost date. You want to be able to move it to a sheltered spot if late frost threatens.

I massacre the rootball when planting rhodies and azaleas. Most other plants too, especially if they have a really dense root system with circling roots.

If you can dig. I bought bags of mulch that had frozen chunks about 8 inches around here in MI. 28 out this morning.