I've grown so accustomed to packing for myself and the kids when I travel (which is a ton of work!) that I'm always surprised to only have one piece of luggage to check-in and one carry-on when I travel by myself. I went on a much needed girls trip last weekend and was pleased to find that my suitcase wasn't overweight from the extra kid stuff - even on the flight back, despite my shopping indulgences (and mother's guilt for being away).
When travelling with my children, I prefer to pack everything in one suitcase to help avoid forgetting bags at the airport. I also choose accommodations that have good, reasonably priced laundry facilities so that I can pack fewer clothes. Forgetting to pack extra baby food or my cell phone charger has never been a big deal since I tend to choose places to stay that are close to stores. But I would rather not to have to worry about things like whether or not I will find the right size nipple for my baby bottles at the local grocery store (that's annoying and super stressful).
After forgetting to pack a few things for my baby once when we went on a family holiday, I created this packing checklist to use the next time we went away on vacation (and over and over again). I find that it's always easier to remove things from a list than add to it - so, depending on the length of the trip, itinerary and amenities available, you can always scratch things off. I hope you find it helpful. Safe and happy travels!