Hi carynoob,
Gosh, all but one of these plants require more sun than it sounds like you might have, if I'm reading correctly. The Aucuba, I think, would do all right in less sun. Are your trees pines by any chance? They are good at letting in enough dappled sun for Camellias and they would get large enough to provide screening.

There's a great website below with tons of information if you haven't already seen it. I'll include the link. I can't think if any trees that will do well with little sunlight as they have to have it for photosynthesis.

Here is a link that might be useful: NC Cooperative Extension

If you decide on camellias and are not too far from the Sanford area there is a great nursery called Watsons. They have a very nice selection of camellias at fantastic prices. You can purchase a healthy four to five foot plant from 12-15 dollars. I just purchased a couple in full bloom. Gorgeous. Adele

Plug for Carolina silverbell (halesia carolina)...not planted enough in our state(s), friends!...and so much to offer.

Here is a link that might be useful: Silverbell Info

This link may be a good one. I second the suggestion of Carolina silverbell. That's one I plan to plant. I didn't see any when I was at Homewood recently.

Here is a link that might be useful: NCSU link to understory trees

The NCSU link is a good one - HOWEVER, I would avoid a couple of the suggestions: mimosa is pretty invasive, and may make the "Noxious weed" list soon, if it hasn't already; all of the Callery pears, Cleveland as well as Bradford, have invasive tendencies, and are prone to splitting apart after 10-25 years; and if fireblight is prevalent in your area, hawthorn, as a member of the rose family, is susceptible to it - it won't kill it, but it's unsightly. I know the list comes from a respected source, but sometimes these lists are simply copied from old lists and not updated as new information comes in, and sometimes the left hand has no clue about what the right hand is doing!

If your yard is shady you will want to buy large shrubs. Plenty of things will survive in those conditions but it will take a lifetime to get any size on them. Most of the stuff I've planted has survived my shade and deep shade areas but I get few flowers and almost no growth. Often the stats quoted on the sites that recommend plants are listing measurements in ideal situations. If your site isn't perfect you have to tweak the numbers.

In my yard the best grower/filler/bloomer in my shade is the hybrid Calycanthus (Sinocalycalycanthus) raulstonii `Hartlage Wine' - it out performs just about everything. A close second is the native Illicium.

Laurabs, I found a 5' silverbell at Page Road Garden Center in Raleigh just over the weekend. They were only $20!...quite a steal. Very nice place with lots of good choices.

Here is a link that might be useful: Page Road Garden Center