[Otter74]

How old are your sons? Are you talking about one 55L pack for all three of you? Or will they be carrying their own stuff?

Half a trip's underwear plus one and wash it in your bathroom sink (or send it to a laundromat); two pair of shorts/pants, maybe three. Shirts for every other day (wash if needed); socks ditto, unless you wear merino (I love it) in which case two is probably fine; one pair of shoes; a hat if you like; large Dopps bag for toiletries; jammies, whatever you sleep in; and whatever else you like to carry on such a trip. I could probably fit it all in the bag that motion linked to. I love traveling light.