Cedar Point is a great hit for the whole family, with a spectacular mix of coasters, thrill rides, smaller rides, and great things for the kids, as well as shows and such for the less adventurous members of the family. That would be my top pick, certainly. Definately a 2-3 day event if you've never been, so that you don't miss anything.
Islands of Adventure has superb coasters and fantastic theming, but if you're looking for a lot of rides I wouldn't recommend it - give it a few years yet to grow. One day would really be sufficient here, unless you pick mid-July or August when the crowds will be heaviest, perhaps.
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Po!nt of View: A different look at Roller Coasters.
http://www.crosswinds.net/~justmayntz/thrills/index.html Don't forget to check out the FEATURED COASTERS and VOTE in the POLL!