It doesn't matter what the liquids are. They just have to be less than 3.4 oz and all fit in one gallon size ziploc bag. You can have one ziploc bag per person. It can be all shampoo if you want. The ziploc cannot be larger than one gallon.
It's actually a one QUART baggie, not one gallon...
Here is the TSA webpage with the rules for liquids in your carryon luggage:
http://www.tsa.gov/311/index.shtm
You get one 1-quart plastic baggie each. All of your carry-on liquids and gels must go in the baggie, and each container must be 3 oz. or smaller. A 6-oz tube of toothpaste that's half empty won't be accepted.
There are
no restrictions on liquids in your checked luggage.
What I usually do is carry a small travel-size bottle contact solution, eye drops and deodorant in my carryon to get me through the travel day, and then put my regular supply of bodywash, shampoo, contact solution, mouthwash, etc in my checked suitcase. Look for the empty 3-oz bottles in the travel section of the store. Even though I put them in my suitcase, it's easier to fill those with shampoo and bodywash and only bring along what I need, rather than lugging along the full bottles (and the space and weight they add up)
A tip: any liquids in your checked bags should be sealed up into large-size ziplock bags. It's not a TSA or airline requirement, but it'll save many headaches if one of those containers leaks or breaks during the trip. Otherwise, you'll have a lot of laundry to do right when you get to your hotel.
For a weeklong trip, I only use one large suitcase and one backpack. In the cooler months I've been fine with using what I bring, but in the sweaty hot months I find that I need to do a single load of laundry halfway through my trip.
Almost everything goes in my suitcase. My backpack only contains the travel liquids I mentioned above, a change of shirt, travel documents, reading material, and most recently my netbook (it's like a laptop computer, but smaller and lighter). In the cooler months I'll also include a jacket or sweatshirt, and if it'll be rainy on travel day, I put my umbrella in my backpack rather than the suitcase. The backpack fits just fine under the seat in front of me, so I've never had to worry about the overhead bins.
With Southwest, you're allowed *two* checked bags for free per person. If you can get all your clothes into one suitcase, I'd stick to that and limit the hassle of two suitcases. Of course, I usually to deal with taking the subway to/from the airport, so two smaller suitcases would be a pain. If I were getting dropped off at the airport, though, I might think differently and pack more clothes.
What I usually do is pack a collapsible duffel bag into the front pocket of my suitcase. That way I can use it if I end up buying more souveniers than will fit in my suitcase.
If you're flying with someone, I'd suggest you each take a change (or two) of clothing and putting them in the other person's suitcase. That way if one of your bags is delayed by the airline, you still have a change of clothing in the other suitcase.
Lastly, if you pack two suitcases, are staying at a Disney hotel and using the DME luggage service on arrival, you'll have to call DME and request additional yellow luggage tags. The automatic mailing they send only gives you one tag per person.
-Rob
