I would get a nice clumpform paper birch. They are always more impressive as a clumpform and less apt to blow down in high wind. There are purple leaved varieties now as well, like Articfrost. These purple-leafed varieties are stunning when larger. The leaf color is similiar to a Crimson King maple but on a birch tree. Never plant a Norway maple. They are the most invasive plant of all hardwoods and they will dominate your lanscape after 10 years or so. Most nurseries will not sell them now because of this. The Amur maples are a smaller maple with an orange color in the Fall. Make sure not to buy the dwarf varieties as they stay rather small.I have two full size Amur maples and they are very hardy, and not too large. The true red or sugar maples are great trees and you could tap the sugar maple to make syrup after it is large enough. Most red and sugar maples are indeed, red in the fall but conditions and individual specimens can be lighter or darker. Oaks are very slow growing and not as red as some of the maples. Remember, clump-forms on the birches and they will offer you more shade and tree strength. A mixture of Serviceberries, Red or Sugar Maples, and birches will be impressive. If you plant in the early spring, keep an eye on The Weather Channel during the first season to watch for drought in the area.

Gray Dogwoods sucker so much that they end up growing in a dense thicket. I think you could plant them 2 feet apart and be OK. In my fields the gray dogwoods stems are about 6 inches apart. I'd expect Elderberry to grow taller that Gray Dogwood and not sucker or spread as much or as rapidly. I would give the Elderberry some separation from the dogwood - don't plant a dogwood within three or four feet on either side of an Elderberry. One drawback to Gray Dogwood as a screen is that they are deciduous - in the winter they won't provide much screening. Same goes for Elderberry, which are even less effective as a winter screen because they have far fewer stems. I think you will see lots of birds eating the berries of both shrubs. Both shrubs will fruit much better in full sun than in shade. I have Gray Dogwood growing throughout the woods, but see little fruit on the shade-growing dogwoods. Same goes for Elderberry. Both need about half sun to grow much fruit. If you have lots of shade you should consider a different shrub. Mapleleaf viburnum (Viburnum acerfolium) would be a good choice, although it doesn't grow upright like Gray Dowood - it tends to sprawl.

I don't have any personal experience with propagating Gray Dogwood, but I've found info on just about any plant I've looked for in the website from the USDA Forest Service and the University of Idaho, linked below. Just go to 'Propagation Protocol Database' and then 'Search Protocols'. A quick google on "gray dogwood propagation" also brought up good info from U. of Florida Here is a link that might be useful: Native Plant Network

Grey dogwood never gets tired of sending up suckers, the suckers eventually get as big as the plant. So unless you want a gazillion plants in one spot, you have to remove them. What you do it dig down about 6 inches or so, a few inches away from the sucker. You'll find a very strong horizontal root running in a straight line--the main plant sends up new suckers along that line. It's easy to see, because the suckers are often lined up in a row. If you want to slow the plant down, dig up that whole horizontal root. Each sucker will be easier to establish if it has a part of that root along with its own root system. The sucker's own root system will be rather small. Plant as for any bare-root tree or shrub--dig a hole or slit just big enough for the roots, don't amend the soil, firm the soil very well around the roots, water well, and keep the area well watered for the entire first growing season. If you're going to dig and replant these, do it before the weather gets too hot.