I'd start browsing Craigslist.
Give yourself, say a $400 budget for 2 bikes. The hybrids aren't bad... other than the coaster brakes.
Put a few miles on them. Perhaps keep to parks and MUTS (multi-use-trails) to start with.
I'm not sure about coaster brakes. Perhaps some ancient 3-speeds will have them, or some beach cruisers, but I'd still try the normal handlebar brakes. You could build a bike around a coaster brake system, but it would be somewhat limiting.
The two of you may decide you don't like riding at all, so start cheap. If it is what you want, then go hog-wild on your next bike purchase.
Hmmm..
Here is an 8-speed coaster brake internally geared hub.
http://www.hashtagbikes.com/product_p/hu7853.htm
And a 9-speed coaster brake hub
http://www.sram.sinocontact.com/sram...-coaster-brake
So, you could build a nice bike around the coaster brake hub, or somewhere the bikes should be out there. However, it still is a big limitation as one moves towards performance bikes. I'd still do coaster + hand brakes.