They really aren't that far away from their family when you consider that they can just apperate home anytime. On that point, why is it so expensive for the family to travel to Egypt? Bill and Charlie could always apperate home and with Molly and Arther, use slide-along apperation to bring the kids back. They could even borrow a tent so they don't have to pay for an inn or be a burden on anyone. They could also shrink and carry or owl their food ahead of time so they wouldn't have to buy anything.