I normally pack for the entire trip but the past couple of times we've stayed longer and packed lighter and just ended up doing laundry. We leave in a few days and we'll be doing laundry again this time. We aren't big pool people, otherwise I would do what others have suggested and do your laundry when the kids are swimming. I try to do it first thing in the morning after we've had a late night (so the kids are sleeping in a little). Otherwise, we come back early from the park and do it then. Basically, you want to do your laundry when people are at the park. If you wait until night when everyone is coming back from the parks, it's going to be more busy.
Another tip, pack with your loads in mind. What I mean is, I pack with the mindset of lights and darks and avoid things like packing two red shirts that need to be washed separately or packing things that need delicate cycle.
Debbie