Organization and flexibility are key. Having a schedule for work week/perfection week or whatever you call it is key. You're better off to tell people exact times when they will need to be there - an longer than you think it will take. We get much more upset if we have to stay longer than we thought than if we get out earlier.
One of the major frustrations I have seen within chapters concerning rush and the rush chair is perceived unorganization. Remember, perception is reality, most of the time. Have all of you stuff planned for a formal fall rush before you leave for the summer. Things can change from there but if you have all you planning in place and you sisters know it things will go a lot more smoothly.
Be organized, but be flexible enough to change things if needed.