"And the "designers community" seems to have agreed to make today's most popular sites share some of these criteria."
I'm NOT trying to argue with you for any other reason than to share opinions... but I still happen to feel that Web2.0 is hype. And if there are a lot of sites following the extremely trendy hype, I personally am thinking that they'll be changing their minds soon enough.
Think about when Flash first came on the scene - I think that's the longest running, overly trendy thing that has ever been brought to the world of design. People have way overused it, and the search engines have only credited sites that started without it, got the attention without it, and then later changed their entire site structure to encompass only flash. You can no longer buy a domain, build a site entirely in flash, and get it to do anything for you.
I realize that AJAX and other aspects of Web2.0 are different, and as of yet have no negative effects on search engine placements, but I still think it's just a passing fad, garnered to "liven up" the design/dev community.
Now, that said - as far as finding a theme for your 11 y/o daughters, I'm in complete agreement that a theme with rounded corners and pastel colors and large fonts is ideal for you! Whether it should be labeled "Web2.0" or not is another story... ;)