Anthony, do not skimp on valving.
Buy Full Port ball valves.
Every circulator should had a Full Port ball vale on each side of it to allow for easy removal and replacement of it.
All zones should have their own valving also.
Install boiler drains on each zone to allow you to drain the zone if there is a problem in the future. One on the return and one on the supply.
Install Key Vents or Coin Vents at every piece of radiation equipment to allow for bleeding the air out of the system also.
Look into a true recirculating loop on your DHW to save on water. A true recirculating loop needs a return leg to feed the water back to the water heater. There are a few systems out there that use the cold water piping to feed the hot water back to the water heater, all those systems do is switch the waste from waiting for the hot water to get to the faucet, to waiting for the cold water to cool down. Since you are ripping and tearing to install the zones for heating than you could add the recirc leg right now also.
Asa to DHW production, a stand alone boiler mate type system would be alright, a plate or tube heat exchanger (w/controls) installed to heat the water going into the water heater and maintain the water temperature in the system would also be okay, as would the DHW coil in the boiler.
Since you are outnumbered in the household you should plan for massive hot water use in the coming years before it becomes a tie again.
Remember. It is better to spend the money now and install valving than to have a leak in the system in the middle of January on a Sunday night @ -8°F and have to shut the whole system down until you can get the parts to repair the leak.