Kenin, do a search for "colonial Williamsburg + landscaping" to begin your research. Many ideas and plant lists to be found there which should be helpful. Then to the library to study the numerous picture books written about Williamsburg. Of course, a trip to that beautiful restored community would help you to see ideas and firm up your final planning. Colonial landscaping is pretty straight forward; low hedges, fencing and squares. A study on site at Williamsburg will quickly illustrate how this all goes together.

I am a garden designer that creates period gardens in the Lehigh Valley and I agree with the above post. There is a book written by Denise Willes Adams that lists the appropriate plants for each period. Try to use local garden centers for the plants (not catalogs) they will be more hardy. You are lucky that there are many great garden centers in your area. Good luck!

I highly recommend going to Colonial Williamsburg for a visit if it's at all possible. I went there early last fall, was truly impressed. I took lots of pictures for my garden, along with bringing 2 sets of the cannonball gate closing systems for the gates in my garden.
Good luck...

http://www.pennsburymanor.org/

as far as practical colonial landscaping with an eye to 'providing' the needs of a large gentleman's farm, you can't beat the place that Bill built, though he didn't get to live there long.

Andalusia down the river a bit has more formal 'gardens' and is a bit closer to the 'federalist' style, rather than good old Bucks County mudstone, but it's well worth the trip, and they offer a bit more in the way of gardening workshops.

if you have 'any' outbuildings on the property, there's a local cat who does english-style cottage gardens (Thomas's?) I think that would be a great tie in (us being one of the english colonies)

also not to be missed are the tulip gardens at Lenteboden just north of New Hope - they're just showcase gardens, but some of the heirloom strains would still work today.