You probably want lower plants under the windows. Both hydrangeas and rhododendrons like acidic soil. I am guessing your soil is not very acidic. The easiest way to make the bed would be to use a raised bed. This will accomplish two things. It will allow you to build up the grade so that water drains away from the house and your new plants. It will also allow you to bring in neutral or acidic soil and mix powdered sulfur and conifer (pine) bark fines with the soil to make it acidic. Rhododendrons have shallow roots so building it up 6 to 8 inches is adequate though 10 is better since there may be some settling.

One word of warning, hydrangeas need a lot of water and rhododendrons don't like too much water. Hydrangeas are the first to wilt in hot dry weather and will tolerate fairly wet conditions. It looks like you have a very small swale between the two windows on the left. That would be the better place for a hydrangea.

Rhododendrons like slightly moist soil but will die of root rot if the roots are kept wet, especially in hot weather. Some people recommend using aluminum sulfate on hydrangeas to make the bloom blue as opposed to pink, but aluminum sulfate will eventually kill many other plants like rhododendrons and azaleas.

Whatever you do, mulch the soil with 2 to 3 inches of oak leaves, pine bark or some other organic material. The article below recommends wood chips, but they have the nasty habit of harboring a "artillery fungus" that shoots tar like balls onto your house that are nearly impossible to remove. A mulch conserves moisture, and keeps the roots cool in summer and warm in winter.

Most azaleas that do well in your area are deciduous so you probably want the evergreen rhododendrons. The shorter, 2' to 3', rhododendrons would be better under the windows. I recommend:

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English Roseum, rose pink, 6' in 10 years.

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Haaga, pink, 3' in 10 years.

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Nova Zembla, red, 5' in 10 years.

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PJM, lavender-pink, 3' in 10 years.

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Purple Gem, purple, 2' in 10 years.

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Ramapo, purple 3' in 10 years.

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Roseum Elegans, rose-lilac, 6' in 10 years.

Hydrangeas are deciduous, so they are good for summer color, but not for winter foliage. For hydrangeas, the oak leaf hydrangeas get very large and need a lot of pruning. An exception is "Pee Wee" which gets 4' tall. A couple of hydrangeas that bloom all summer are "All Summer Beauty" and "Endless Summer".

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Pee Wee

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All Summer Beauty

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Endless Summer

Good Luck!

Here is a link that might be useful: Growing Rhododendron and Azaleas in Illinois

Thanks Rhodyman - height isn't really a problem, the bottoms of those windows are 7' from the ground. Yes we were planning on bringing in more dirt. Until we got the gutters on, we just let everything sink and settle and the dirt level will be brought up to the bottom course of brick (right now you can see some of the concrete footings) and then sloped out into the yard. Question though, which would prefer more sun, the hydrangeas or the evergreen rhododendrons? There is more sunlight further to the right. I am leaning towards putting a hedge of annabelle hydranges from the AC unit left to the weigelas and possibly rhododendrons to the right between the AC unit and the deck. I could build the soil up a little more on the right on the deck side so their feet dry out as needed. I didn't know what to amend the soil with to help the pH - what pH am I aiming for ideally? You have pictures of rhodies I have never seen. I have to drive an hour either to Peoria or the Quad Cities to get to a nursery center but even there I do not see many outside the good old boys that everyone plants. I'll do some research on the ones you listed. Thanks.

Hydrangeas actually take sun better. Rhodies like partial shade. However the ones I listed are tough and take sun fairly well.

Most of the rhody pictures came from the Monrovia website so big box places may carry them. The only problem is that big box places quite often kill good plants before people buy them. www.greergardens.com in Eugene, Oregon, sells mail order. They have frugal-dendrons

A pH of 5.5 to 6 is good. For amending the soil, any conifer part is good like fine pine bark particles, pine needles, and even conifer wood chips used in moderation. I like composted peat but it is hard to find. Pine bark dust is easier to find around where I live.