Matt,
For maximum comfort during the heating season you want the supply registers down near the floor and the return(s) (roughly equal in size to the supplies) also near the floor. During the cooling and dehumidifying season you'd want them all in the ceiling with the capability to open or close them depending on the season. This is ideal if someone is actually going to live in the basement (like a bedroom). If the basement is just for occasional use then just try to balance the supply and return and be sure to wear shoes or slippers during the winter. If the return is less then the supply then you'll suffer a bit for comfort and the conditioned air will try to go upstairs or up the chimney if you have an older furnace Don't put the return(s) too near a supply vent. Many basements don't have any return so some is better than none.
My Minnesota 30-year-old rambler basement stays in the mid sixties throughout the year and I don't condition it, although it is setup for it and is insulated. The floor is cold (mid 50's year round), but I only use it to hide from the rest of the family. If it was too comfortable, it wouldn't be a good place to hide. When I put in a new furnace a year and a half ago I discovered that the returns in half of the upper house (entry, kitchen, family and living rooms) were not connected to the furnace. (Must have been a bad day for the HVAC guys.) Strangely enough, I also had a 3" return drawing air directly from the attic and I closed that off. Connecting things properly did improve the comfort and energy savings in the house during both seasons. I run the heat pump till it hits 20 degrees F and have been saving a lot of money there as well.
Good luck with the project. I think you are on the right track.
dss