Red clay can be great to plant and garden in with the addition of some good organic matter. Coffee ground should make a tiny contribution to that. I suggest bags and bags of what is called Soil Conditioner at Lowe's, or a similar product. It's simply a ground bark mixture. Triple ground mulch would be great, composted sawdust, chopped leaves, etc. Be sure to plan for an attractive organic mulch once the planting is finished. Don't work the soil if it is soaking wet. Don't listen to anyone that suggests you add sand to clay soil to 'improve drainage'.

Hydrangeas require some shade in the south. I would have thought that Charlotte would be outside the hardiness limit for Indian Hawthorn. My experience with it is strictly in warmer SC, and where I live now (Huntsville,7B), it is rarely seen and never thrives. It requires full sun to do best, by the way. I would so some research on that plant, however. I'm sure someone from this area will check in with some very helpful comments.

Since you know little about plants that can be expected to do well in that area, I would avoid Lowes' and Home Depot. Those stores are rather universal in what they stock. You can buy spruce in Hilton Head, SC, for example!!!! What a laugh. Visit the locally owned garden centers, and TALK to their managers. In exchange for being able to pick their brains, give them some of your business.

Also, look at the architect's plant choices with an open mind. Most (not all) landscape architects have very little practical plant knowledge. Sad, but true.

There are numerous hollies worth looking at, and a wide assortment of other broad leaf evergreens. You could observe these at the garden centers, though I sure would find a good book or two. The attached link from NC State is a pretty good tool, too. If you click on the 'shrubs' category, you can enjoy a bunch of fact sheets. Check out Rapheopepis indica (Indian Hawthorn).

Here is a link that might be useful: NCSU Fact Sheets

Ask your sister and BIL what kind of shade they get on the east side of the house (other than the house itself). Sometimes houses are so close together that east facings barely get morning sun.
We have loropetalum on the east side and it's easy to maintain to the height desired and it's evergreen. Grows well here and there are several varieties with either green or maroon leaves. East facing foundations, so long as they have real pitch for drainage, would hold dwarf burford holly , weeping yaupon holly (tall), osmanthus(tea olive,fragrant flowers), pittosporum (solid green or variegated), various viburnums (flower and berries). A protected spot with excellent drainage would be nice for a winter daphne although you have to plant them very high in the soil.

East might be a decent location for some gardenia shrubs too. She can tuck in shade loving annuals that tolerate the morning sun.
You'll know more once you get here as to drainage, sunpath,prevailing wind direction and general air circulation.
What part of Charlotte will you be visiting? There are many garden centers but there are one or two 'best' in each direction.

Endless Summer hydrangeas have had mixed reviews this year.
She might try potting one up and placing it where she wants it (or where it wants to be).
If she's dealing with new construction landscaping, know that most of what they claim as topsoil in beds and borders is simply construction subsoil. Nearly devoid of nutrients. First order of business is to have the soils tested and then amend them as required. She can have that done in advance of your arrival.
Before she invests in a japanese maple know that its siting is critical for its survival. Many of the varieties just won't take if exposed to our hot afternoon sun and heat reflected off the house. The red broadleafs are more tolerant, the laceleafs the least tolerant.(in my experience)
As for landscape architects..the ones I've dealt with fail to take into account sunpath, existing drainage, nearby houses, nearby trees etc. etc. They know their plants latin names and what seems to thrive in Charlotte but fail to remember that they won't be doing the installation. Uneducated and uncaring crews can doom the best planned landscape materials.

Thanks to both of you for all the great information; this has been very helpful! I appreciate it.

Don't expect Endless Summer to bloom constantly all summer -- it is a repeat bloomer. If you are dealing with more sun, go towards Annabelle, an arborescens, or Limelight, a paniculata. There are a number of great mopheads and lacecaps -- Endless Summer has gotten the most play. See Michael Dirr's new hydrangea book for his top 10 suggestions or go to the American Hydrangea Society's website.

Waterfall is a beautiful green Japanese Maple. Bloodgood is probably the most reliable red, though don't count on it staying as red in the summer as in the north. Red Select and Crimson Queen are good cutleaf, lower growing varieties.

Young's and Rountree Plantation offer the best selection if you are south of downtown; if you are nearer Lake Norman, visit Dearness Gardens in Huntersville or Farmhouse Gardener in Statesville. Home Depot and Lowe's offer some values if you can get them coming off the truck before they manage to kill them.

Little Rascal Holly is a patented plant that offers a feathery dark green foliage with maroon new growth that will stay under three feet. It is far superior to your other suggestions -- Otto Luyken is prone to root rot and Indian Hawthorne is great to feed the deer with.

Plan on improving the clay soil by at least a third with either soil conditioner, mushroom compost, compost, or some combination thereof and till deeply. They don't call us the dirt poor south for nothing.

Late March is an ideal time to plant shrubs, trees, perennials, groundcovers, and vines but too early for summer bulbs or annuals.

Happy gardening,

Larry

Larry, Thank you for the wealth of info!