I need an idea of how to prepare potatoes for Thanksgiving. I like to have both sweet and baking potatoes.

Gratin!!! You could do 2 separate ones, or mix sweet potatoes with normal ones. Or a nice crispy rosti would fit right in too.

My current favorite grillhouse makes a mashed sweet potatoes with both sweet and white potatoes, maple syrup and butter. It's really good.

Here's a really delicious squash and potato recipe with crushed amaretti cookies on top
http://www.marthastewart.com/355415/mashed-squash-and-potatoes-amaretti

Lots of good ideas for sweet potatoes on the NC website http://www.ncsweetpotatoes.com/ If you are looking for something healthier than the usual casserole, try the roasted wedges with parsley salad http://www.ncsweetpotatoes.com/recipe/sweet-potato-wedges-with-parsley-salad/

You could do both mashed white potatoes and roasted sweet potatoes. For the white potatoes you could try a roasted garlic variation found here: http://food52.com/recipes/12361_roasted_garlic_mashed_potatoes and Orange Cardamom Roasted Sweet Potatoes: http://food52.com/recipes/9245_orange_cardamom_roasted_sweet_potatoes