Dear Maple Leaf,
There's not much I can add to Sherri's (typically) comprehensive post, but I can reiterate her point about lifting. My youngest daughter was 8 going on 9 when I had my surgery. I'm only a Daddy, and wasn't responsible for day-to-day cooking, etc. But I had a lot of trouble with lifting during my otherwise smooth recovery. I remember that my daughter quickly noticed, and began pouring my water for me, to save me the pain of lifting a full pitcher (and yes, that help came in handy).
Beyond that, another thing to consider is what/when you tell the kids. Do they already know and (more or less) understand everything? I was quite secretive about my plans to donate (nearly two years later, I've still told very few people), but as it happens my youngest was one of the few to know beforehand--since she still lives at home, she heard her mother and I make some references to the hospital. So I took her aside and gave a fairly simple explanation, remembering to give her time to digest it and formulate her own questions. As bright as she is, she didn't really need to hear about all the epidemiological studies on post-donation health, and she definitely was not interested in too many "yucky" surgical details, so I kept it simple, and that seemed to work. She's been wonderful about keeping the secret, as well. But, as a rule, I've learned not to assume that a child actually registered the precise message I thought I was broadcasting, so it's probably a good idea to offer the kids various opportunities to ask questions.
Good luck to you!
Snoopy