J.L.
I think a side preference is definitely normal! I also think it's normal for one to produce more milk anyway - my right side is the preferred one in this house! My DD loved it most and my son does too .. LOL You might try pumping on the other side if you're really wanting to "keep up appearances" and for them to appear more normal!
As far as your second question - I just let my daughter lead the way when she was that age. She didn't actually start weaning until I became pregnant with my DS when she was about a year old... she just started cutting out a feeding on her own. Eventually, at 14 months, she just wanted to nurse right when she woke up and by 15 months she self-weaned completely. If cutting out full feedings is a problem with engorgement, I'd suggest maybe just lengthening the time between feedings instead. That way you're only going, say, 4 hours between feedings instead of 5 or whatever the case may be. :)
Hope that helps!!!
When my DD weaned herself, I experienced no pain and no engorgement. :)