Thanks again for the posts and suggestions. I did end up using mine and my wife's United Mileage Plus accounts. We never check luggage, so the free bags thing was not very important to us (but thanks PVDtoDEL for the tip). We did get full miles for each segment - both netted exactly 12,546 for the entire trip.

I had to manually add the UA Mileage Plus numbers when using the check-in kiosk for our last leg home, but other than that I think Expedia passed along the info correctly (I was careful to make sure, though).

Thanks again!

David