I know I am going to be a real downer when I say this, but really think about if the receivers of your gift bags are going to appreciate your time, effort and money. Will you be sad if you don't see or hear nice thank you's, or at the least see some smiling appreciative faces?
I have found, over the years, that some folks are just not that into gifts. Usually the kind people who love to give gifts, are the same ones who enjoy gifts. That means a small token gift really means a lot to them.
Many people do not get the whole token gift concept. This is especially true of men. They think, "What am I going to do with this?" They may not want to wear the t-shirts you make, or even find them uncomfortable. (My husband and I have huge heads and t-shirts of any kind always choke us. My brother's head is so large, for him to wear a t-shirt he has to cut out the neck hole.)
On top of all that many parents get upset when their child is given, "One more little thing for me to pick up." They don't see the fun value of a little toy to play with on vacation. All they see is something that could get broken or lost.
For the 13 year old I would stick with a Disney gift card and let him choose his own gift. For the little ones I would find something quiet for them to do in the room, maybe a coloring book and crayons. (This is great for wind down time before bed.)
If the rooms have microwaves maybe popcorn for the older children who will not choke. If you truly want to gift the adults, maybe you could give a gift card to watch their children so they can have a bit of alone time. (Alone time for adults sure is hard to come by at Disney, and often you need to catch your breath and regroup.) Maybe you could coordinate and pay for a pizza party. The cost of those little gift bags will add up.
As for pins, though I love the idea, I would not do that. Many families do not want to get caught up in pin trading. By giving out a pin you may start a pin trading fever that the parents will not appreciate.
Like I said, I know your heart is in the right place, but I have heard so many stories on this board and I just don't think people will appreciate your efforts.