Hello, Chris. My only concerns with your requirements are: 1. quick growing and 2) irrigated but a little dry nonetheless.

The Ackermand Hybrids tend to bloom early, that is, during the Fall so winter should not affect the flower buds. I do not grow them here so we should let some Zone 7ers chime in with specifics.

Most camellias are slow growers. As far as soil moisture, you will need to water more often and especially until the new plants become established (1-2 years). This should not mean a lot of watering though. It means to water again when the soil feels almost dry again to a depth of 4".

If you cannot do this, I was wondering.... how come you do not plant another set of hollies in the same area? You said that the kids have outgrown the playset sooooo....?

Your problem is not winter cold or partial sun conditions; camellias actually like filtered sun. As for cold, camellias should be perfectly hardly in D.C.. I grow the so-called "Kumasaka" variety--supposedly one of the hardiest (should be hardy to NJ., Long Island, and beyond on the coast). (I just today expanded my camellia collection.) Your biggest problem is dryness. I would work to really improve the soil conditions before putting the camellias into the ground. I'm just getting into camellias myself so I'm not an expert but I do know that they like moist, acid soils that are well-aerated. They are also surface rooters so a nice layer of mulch is helpful year-round for cold and heat. Into my soil (tends to be clay), I worked some gypsum, peat moss, humus, and holly tone (good for acid plants). Will probably also use the camellias as a new place to recycle my coffee grains (acidic). Once you get your plants in the ground, make sure you keep them well-watered until they get established. I am using mine to create a privacy hedge but have left the current planting (combo of privet and viburnums) in place, in order to provide some protection from western sun exposure (off a driveway). Also, camellias are at best moderate in growth rate (not fast), so this way I have some privacy and protection for the camellias before they get big enough to do the job. Good luck!

The camellia collection at the National Arboretum was decimated by a cold winter some years back. You might want to go look at what they have there now to see which camellias are liable to be more hardy - or what other kinds of shrubs you might be able to use instead.