Here's our situation. We are a one-car family of two parents and two boys, ages 7 and 9. I bike to my office job; my wife combines being a stay-at-home mom with a fine art and graphics career. So she is the primary car user, for grocery trips, general errands, and schlepping art around. Her cycling is limited to short recreational rides with the family on back streets and trails, using her classic Schwinn 3-speed that she's had since she was 15.

She was just complaining to me last night that she never has time for exercise, especially during the summer when the boys are on school vacation. I suggested we could get a bike trailer to enable her to do some trips by bike, especially for groceries. To my surprise, she is open to the idea. So now I need to decide what to get.

I'd personally love to get an Xtracycle, but we are of fairly different heights, so we couldn't share a bike comfortably, unless maybe it was primarily her size but rideable by me if I jacked the seat way up. I wonder if any frames are more conducive to that than others?

If an Xtracycle is out, that leaves a trailer. I'm imagining that she would get to the grocery store through the back street route, which also involves a short distance on a paved pedestrian path. (The alternative is a busy shoulderless 4-narrow-lane road, which I'm pretty sure she would not ride because she's not comfortable in traffic. Although that street also has a paved sidewalk/path next to some of it.) The terrain is mostly flat, one or two small hills.

I know some trailers are 2-wheeled and some are 1. I've heard that 1 wheel handles better and can go more places, but how are they on carrying uneven loads? When you are stopped, does the weight of the bike keep the 1-wheeled trailer upright, and does that produce a noticeable pull on the rider? How about packing it at the store without tipping over the bike ('cause you're not on it at the time)? What can you recommend for trailers specifically for loads such as groceries? (We don't need a kid trailer; the boys are too old to ride in it anyway and have their own bikes to ride along with Mom.)

If it matters, once every couple of years, I have a need to fly somewhere on business, so I would also take advantage of whatever trailer we buy to bike to the airport with a suitcase. I suppose anything would work for that.

Thanks for any advice.