Depends on which day you go, but I'd do 2 days. I think if you went on a weekday, and really rush, you could. We went 2 days during our week at Disney, the last week of Sept in 2010. We did the one park Tuesday, and IOA thursday. We had NO problems- but didn't think in a million years it could be squeezed into one day. But we also have 3 kids. We have heard some horror stories about WWOHP, but had NO problem. I think the key is really going on a weekday compared to a weekend.