Mini-Splits with Radiators & Geo-Thermal?

We're trying to figure out how to heat & cool an historic pile of bricks.



Built in 1930, two stories, three units, hot water radiators ... mostly broken.



The pipes passed a pressure test, so new radiators and a 92%+ boiler could work.



Or, we could do a geo-thermal heat-pump in the back yard, and duct air from a unit in the attic down, and from the basement up to the first floor. A supplemental water tank would also handle most of the plumbing hot water.



There's the higher expense of ducting & making holes, plus the aesthetic of cutting up old woodwork. ( 30% $$$ offset through the government should certainly help ) There's also the "dryness" issue with both heat & AC coming through cut vents.



So, can we combine the best of both?



Can we use a geo-thermal heat-pump system ( with a 92%+ gas backup boiler ) to handle a new set of radiators, and combine it with mini-split A/C units for cooling in the Summer?



It would probably take 8 mini's to cover both floors. ( The place was previously cooled with 4 window A/C units.



The front of the roof is hipped, with enough room in the attic for a unit & easy venting options. The back part is flat, with enough room left to crawl back & run ductwork. The space above, over the joists, has all been "foamed". There are two skylights up there as well.



There is a clear channel from the basement to the attic & roof via the chimney of an old incinerator. It might be possible to run lines through there. We have "shade issues" that prevent Solar and PV applications from being practical, and little sustained wind, so geo-thermal is our only available "green" option.



Thanks for your time and attention.