I bought an '80s tourer cheap on eBay when I wanted to start riding with my son, and added a $35 Bell child carrier. I keep swapping out things like bars and chainwheels in favor of better comfort and convenience (same was with most older road-ish stuff), and I wish I could get 27" tires wider than 35mm, but so far it's been pretty decent.

Now that the little guy's approaching 5, I'm liking the idea of a kidback tandem ....... supposedly you can kidback starting at age 2-1/2!