We were there July 6th and 7th last year (mon and tues) and the crowds weren't bad at all. I don't remember specifics about wait times etc, but I do remember that it was MUCH less crowded than when we went May 15 (same year) which was a friday morning.
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But I think it depends on what day of the week the 4th falls on. I would think with it being on a sunday that crowds for that week still wouldn't be bad but I noticed that Deluxe APs are blocked monday the 5th so I'm thinking that may mean that a lot of people have that day off from work which would mean a busier park. And then some people who have monday off might decide to take the rest of the week off to have a longer vacation there.
So in other words, last year was great, but not sure about this year. It should still be okay though, especially if you get there at opening every day and collect FPs.