Their vacation home is cute, I'm sure you could get it set up nice and cozy for them as a temporary solution. With a heat pad and maybe partially cover with a tarp to keep out the cold.The only thing i can think about is to set up a temporary shelter in the Duckie's vacation home, i can run an extension cord from the patio and connect a heat-pad for them, but they need at least a little run-area for the day and that's a problem. That cheap-plastic fence
is almost weathered away and won't contain a small duckling.
If I remember correctly your neighbors have chickens...do they have any extra fencing or a pen that you can borrow until the ducklings are big enough to be with the other ducks?