Consider a trim that is straight modern lines, just bigger than the traditional trim. Keep it simple.

Craftsman casings are usually flat. Typically on a doorway if you are going to replicate craftsman style. The piece of trim for the header of the door looks best if it is 5/4" about 5 1/2" wide material with the 'legs' on the right and left side of the doore 3/4" material about 3 1/2" wide. You can go 3 1/2" or 5 1/2" for the base. Typically the base looks better taller but it depends on your style. Base material is usually 1/2" thick.

I wouldn't go with Shaker-style, since it's very flat and simple. I'd go with a moulding that has a slight detail, while still looking modern, not colonial.

The pictures I fell in love with were the Windsor one craftsman collection. They aren't completely flat, and seem to be on the larger side. We only have 8 ft ceilings so I know I can't go too big, but I'm ordering samples and hoping it will blend well with the colonial exterior. Are there any renovations I can make to the outside to complement it?

You will need to post a picture of the outside to get advice about it:) If you have the money, consider talking with an architect about the outside because changes can involve structural issues.

We also changed out our hollow core doors to paneled doors. If you have hollow core, you will want to consider changing them because wide trim deserves a nice door.