Hi Jawine!
I hope you and your little guy can get a tandem; they are just ideal for riding together.
The one I got was used at time of purchase, and it has worked out very well. For a very long time, I watched the annual tandem races put on here in Eugene by Burley Design Cooperative when they were a force in that part of the industry (they have since gone bust and reorganized, concentrating on just trailers in a new headquarters in a new location). Oh, a tandem looked like a wonderful thing from afar (and later proved to be just that), but there's no way I could afford one, so I started haunting the newspaper classifieds (pre-Internet and pre-eBay days). Finally, I found a couple that looked promising. The first one was just shot, found leaning against the outside of a barn. No paint, torn saddles, rust, drivetrain worn beyond salvage...no. The second one sounded better, so I kept leaving phone messages for the seller on the holiday weekend and received a nice call-back on Monday, the seller saying, "You're not the first, but you're the most persistent, so you must really be serious!"
I was.
Turned out the seller was an engineer whose had just transferred here and downsized to a condo. There was no room for the Big Bike and it lived in the laundry room, where the ozone from the clothes dryer was busily rotting the tires. They hated to see it die a prolonged death from disuse (their two sons were grown and about to start college), so they put it up for sale at USD$600 -- a bit less than half the price of new at the time. It was a Rock 'n' Roll model, with 26" knobbly tires and straight 'bars, and I converted it to a touring tandem with drops, mudguards, racks, and road slicks. The sellers were really big people who had successfully ridden the bike in a couple Seattle-to-Portland rides (200mi/322km), so I had no worries about it handling another rider and panniers. The bike needed a respray after regular transport in a pickup truck bed, so I did that, applied new transfers, and I decided to add a few braze-ons and relocate the Arai drum brake torque-reaction arm, and braze-up a brake booster and adjustable stoker stem while I was at it. It's looked fresh ever since, and I've never regretted the purchase (see:
http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=4523.0;attach=1997 ...and...
http://www.thorncycles.co.uk/forums/index.php?action=dlattach;topic=4523.0;attach=2001 ). I've ridden it alone 260km in hilly country a number of times and found it made decent tourer for one. If you choose the size carefully, the rear compartment can grow along with your little one (adjustable stoker stems do wonders, as do long seatposts), and if he eventually is taller, you can swap places on the bike and still use it. Lots of fun, and pretty easy to sell-on if it comes to that.
The nicest thing is being able to converse easily, to see the same things, and to reach the top and bottom of hills together. It is a fantastic equalizer for people if different abilities, and a strong rider can still get a great workout without killing a weaker partner. Riders soon get a feel for when to apply power or pause, and riding partnerships form quickly and successfully through the tension of the timing chain -- you can feel right away when to add power or back off. The Rear Admiral will always outrank the Captain, so it pays to keep them happy by allowing extra clearance when passing bollards, calling out (and avoiding!) potholes (a cry of "Post" give the back-seater a chance to unweight the saddle by standing in time to avoid the shock of an unseen bump), and generally remembering the folks behind can't very well see what's ahead, so it is wise to avoid surprises (and truly excessive speed unless agreed-upon first).
Yeah, if you can find one, I think a tandem would be just about ideal for you and a little(r) one, Jawine! You might shoot an inquiry to Lisa Parsons at Thorn to see if she has any suggestions or might know of a used tandem up your way. She rides with her son, and in the brochure photos, they're having a wonderful time together! Best of luck in your quest to find one. Have you contacted any local clubs to see if a member might be interested in selling? When I was searching, I put out feelers everywhere. As it happened, I found mine in an ad, but lots of people knew to keep me in mind, and that didn't hurt. Sometimes the ideal used bike is right around the corner, and you may not even have to deal with shipping; I rode mine home from the seller's, just over 6km away!
Best,
Dan.