Try
cellsalive they have interactives about all the parts of different types of cells as well as sections about mitosis, meiosis and other related stuff. A search engine that is geared towards younger kids is
Ask they tend to leave out all the higher level sites in their search which cuts down on your weeding out too. This use to be called Ask Jeeves if you're familiar with that older name.
I also just remembered my daughter has a series of books caled The Usborne Internet-linked First Encyclopedia of ________ (pick a topic ). You can get info from their internet links even without the books. Go to their webpage,
First Encyclopedia pick a book topic from the left menu bar and then randomly pick a page number you want to look at and you get a bunch of info. With out the books it will obviously be a bit hit or miss, but it also tells you how you can buy the books.
