The easiest would be just to use a boiler, hook it up to your heating manifold and away you go. I put a ball valve on the input side of each pipe run so I could control flow, which worked fine.
I had an extra water heater that was still good, so I chose to use a water heater and a circulating pump on a thermostat. That way I could keep the water tank at a higher temp to give a surge of heat when needed. The trick with a water tank is you have to make sure it isn’t going to be pressurized or it will explode. You need a surge tank. This is likely not legal in many jurisdictions so be sure to check.
I didn’t use glycol in my system as it was already full of water. I likely should have, and had plans to, but sold it before I got around to it. The risk was only if your system stopped in the cold and burst. Certainly I would have done it if I stayed longer, although water does work fine it could have troubles over time.