Your plan is generally opposite to natural succession. You can do some of it but it is an uphill battle. I think Tsuga caroliniana would do okay, since mine have survived and looked good for many years with a fairly closed summer canopy of maple, oak and sweetgum. I would suggest you open up an area in the woods and the conifers will somehow get there. Build it and they will come! A clearing, I mean.
Our understory in my neighborhood is holly (Ilex opaca and I. glabra), Kalmia latifolia, but rarely a native pine.
If an area is cleared, within five years a red cedar and very dense pine forest has started.

Eastern hemlock is a climax species and naturally grows in shade. Balsam fir might be suitable as well. Thuja occidentalis can take a litle shade but will not look good without some sun.

I'll second Lycopus's recommendations.

If you have deer in you're area (especially during winter and early spring) the only sure way to prevent browsing that I know of is to fence the seedlings. The best solution I've found is to use construction reinforcing wire (the kind that they put in concrete). It's relatively inexpensive and doesn't need stakes. It will rust, so you might not want to use it where appearance is a big concern.

Add some Picea mariana in the runoff swamp.

white pine P. strobus

tamarack would grow well in the sand - we have it in the first succession dune on Manitoulin. There are also hemlock and spruce.

I tried to post this yesterday and it seems to have gotten lost: I like the suggestion for eastern hemlock, which is about the only native, shade-tolerant evergreen tree for your area.

For an understory species, American yew is great, although it is deer candy and will probably need some protection.

Will probably start with sporadic groups of hemlock and balsam. Some marianna in the swamp also sounds like a nice touch. Thanks much
Greg

Just FYI Greg, I will third (fourth?) the recommendation for hemlock as the native plant that grows in these conditions. Look all over the upper Great Lakes, at least in Michigan and WI, and you will see hemlock in association with beech and maple and yellow birch, as an understory tree. I planted about 50 hemlocks in SE Michigan, just south of the native range, in an oak hickory mature woods with sandy soil, and they are thriving. Hemlock does grow in damp soil, swampy areas too, though I have noticed that the larger plants I planted in less well drained soil are not thriving as well as those in acid sandy upland soil.

I like the idea of tamarack near the swamp. I believe it will do well for you.

Bogturtle told you to get Carolina Hemlock. Good luck finding that in a nursury. Eastern hemlock and Red Spruce can out compete hardwoods. White pine would be suitible. Some Lodgepole Pines and Douglas Fir from out west would work but you would have to cut holes in the canopy for them to take hold.