I'm always the out-of-town family person. If you have already ran it by the out-of-towners as far as the two dates, then you are set. Will they have to fly? If so, ask them which weekend they'd prefer. Even though Easter may sound more expensive, last minute tickets can also be expensive. Let them look for tickets first (set a deadline of 2 days so you can make a plan). Do they plan to attend Easter anyway? If so, ask them if they would prefer to do the family shower then.
Then send either weekends' invites out immediately. You can fill out everything else except the date while you wait. Send out an email or phone everyone that needs a longer heads up if you're worried, but don't skip the invites!
Be sure to ask any more questions you have about the shower on here. There are YEARS of experience on this forum!