Uhgg..you have a few nights there that are predicted to be quite low.
I would say with the water constantly moving, you might be OK, but I wouldn't want to chance it.
If you were to shut it all down, would there be a way to drain the water out of the pipes and bring the pumps inside?
When you say the pipes are wrapped, do you mean with some form of insulation? Your probably going to need more than that.
You could go to Home Depot, Lowe's, a hardware store or whatever home center you have near you and buy pre-made heat trace cable. It comes in various lengths and will plug into a 120 volt outlet. If you can, get the one(s) with the thermostat bulb on the end, so you won't waste electricity when it's not needed. Or just unplug it when you feel it will be warm enough.
You'll also need pipe insulation to completely cover everything and duct tape to secure the insulation. You can get the foam pipe insulation that comes with a split down it's length so you can install it easily. It's not expensive.
Here's how to install it:
Don't coil it around the pipe. That's not how it's done. Run it straight and flat against the bottom of the pipe all along the full length of the pipes. You want it on the bottom since heat rises.
Believe me, I'm a retired electrician and have run miles of this stuff. We would get it on reels and make it up ourselves.
Your supposed to use a glass (fiberglass) tape to hold it in place. If you can't get that, then just use a thin strip of duct tape around the pipe. Just use a little bit of tape here and there, just to hold the cable in place. Don't cover it in tape. It is best to use the glass tape if you can get it.
If you get the one with the thermostat bulb, make sure the bulb is securely pressed against the pipe so it gets a good reading.
Once your cable is all run, cover everything with the pipe insulation and seal all seams with duct tape. For the elbows, you can get creative by cutting the insulation to fit properly. Be careful, don't use the knife near the heat trace cable. You don't want to ruin it.
I don't know how long your pipe run is so you'll have to determine how long your heat trace cable needs to be. You may need to use more than one.
If the plug for the heat trace is nowhere near an outlet, you'll need to feed it with an extension cord.
Normally I would never reccomend using any extension cords outside for any length of time, but if you need to in this emergency situation, make sure it is at least 14 gauge, but I reccomend the heavier 12 gauge.
If you use an extension cord, try to protect the plug from the weather by tucking it underneath something. Don't wrap tape around the connection. Doing that can trap moisture and cause problems. If it ultimately has to be exposed, have the female portion facing up. This way water won't collect in there.
Hope this helps.
Next year, think about winterizing your system. Shut the pumps off and drain the pipes. If you can't drain them, blow them out with an air compressor. You might want to do that now and forget the heat trace cable project.
If you shut the pumps down, get an aerator with some air stones hanging close to the surface on strings.
I wish I were there to help you.
Any questions?