I'm wondering the same thing. Thinking about changing a few things around with dining to go to the 2/5. Decisions, Decisions.
Keep in mind that Feb 5 is the evening of Mardis Gras....I know that there will be a LOT of people coming to WDW that week from Louisana (and around there) to celebrate Mardis Gras and the winter break. Now...I've never been to a Mardis Gras celebration in New Orleans....only wished,

....but I do believe it would NOT be an understatement to say that them are some people who knowwwww how to part-tay.
Of course being the middle the week it would probably not have many locals attending, as they'd have to get up early the next morning and go to work (poor slobs,

).
From what I've heard about the P&P parties in the back there really is no such thing as "crowded". I don't think I've ever read a trip report or P&P report or comment where someone went to a past P&P and complained about the crowds. Most comments were about riding the most popular rides over and over, sometimes without having to get off. The "crowds" I've heard about had more to do with the length of the line to "meet and greet" with Captain Jack Sparrow. And even those were often negligible later in the evening and early was less than an hour.
I switched from the 2nd to the 9th because I had originally thought most of those Mardis Gras party-folks would just be arriving on 2/2 and therefore not be going to a late night party that first night....but the thread where everyone posted their hopes for dates seemed to show 2/2 was going to be very popular.....and I figured since 2/9 was our last weekend of our month long trip, it would be a great thing to end our trip on.
I'd say pick a date when your family will be most rested.....these are late nights, lots of excitement and stimulation for little ones....so the more rested they are, the more fun they're likely to have. If you're just arriving from a different time zone the day or two before a party...pick a different date......if you have ADRs for some thrilling character breakfast on the morning of or the morning after a party....pick a different party date (or reschedule the ADR) so that they don't have excitement for toooo many hours.
If you have energizer bunny children, like I do....that can go all day and all night if the fun is worth it....then think about your own schedule. As someone used to being in bed at 9pm (but up at 4am for some me time) everyday at home....I know that I need to sleep in or take a nap the day of the party in order to be able to keep up with them at midnight.
