Our family (small: 3 of us) routinely does only 2 park days b/c we live close and go frequently. However, I tell others who go less, have more people with them, etc. that 3 full days is an optimal amount of time. I'd second that for you, especially if you aren't rope droppers. Standard asterisks: depends on the time of year, what special/seasonal things are going on at the parks, weather, etc. For me, 3 full days is enough to get to do most (if not all) the things you want to do assuming nothing goes awry. I don't think you can go wrong with 4 days either, but my guess is 4 days gets you to re-rides, re-watches, etc.