Instead of buying an inverter, go to a truck stop and buy a coffee maker with the right kind of power cord to plug into your vehicle’s DC 12 volt outlet. Here some examples of what you can find: http://www.roadtrucker.com/roadpro/12-volt-coffee-pot-mpat-979.htm These aren’t very large, but if you and some other parents get two or three of them going simultaneously, one on each vehicle, you should end up with a decent amount of coffee, and you can brew more while you sip on what has already brewed.
It’s amazing how much more efficient it is to use the power your vehicle provides, as opposed to an inverter, which is highly inefficient.
When I was a truck driver, I was amazed at how many appliances I could get for my truck at truck stops. Things like electric heaters, microwaves, and electric coolers can run on a 12 volt outlet easily as long as you don’t need anything to be hot or cold right away. The same goes for a simple coffee maker. It can easily run on a 12 volt outlet as long as you don’t need it to brew quickly.
If you’re not comfortable with this, you can always get a flash pot for your vehicle and make instant coffee.
I still have an AC/DC television, a DC electric cooler, and a DC flash pot from my truck driving days, but they’re pretty useless now. The cooler would take about 24 hours of continuous power to get cold, but fortunately, in a semi, you can leave it plugged in 24/7. In my car, with it getting shut off at every fuel stop and restroom stop, the drinks in the cooler never get cold. The flash pot was good for heating up water for noodles, but I’m not a fan of instant coffee. Instant coffee is like cheap beer. Some may say they like it, but I’d rather have nothing.