I think we're finally done. Thanks to some helpful feedback from the client and other designers, I went one more round and pushed the final design a little further. I pulled it horizontal a little more and pushed some of the size relationships, all with the goal of emphasizing the 'rule of thirds' more. Before, there was a very strong visual line straight down the middle that essentially cut the design in half, and the black ribbon between the words 'sidewalk' and 'monkeys' was too heavy and crossed too many letters, creating visual weight where I didn't want it. I was worried about making the words 'balance bikes' too small, but I think reducing them down helps to have more clearly defined shape relationships and large-small play.
The one color version needed only slight modification, and I think is working very well. I like it on a business card with rounded corners, as I think that plays well with the bike tires, which are the only round thing on the logo.
Thanks again for the feedback, and remember, just when you think you're really done, you're usually not:)