You know, it all sounds like a lot of fun, but I don't want to "overbook" our week with meets / exchanges / etc... so I'm just gonna 'talk out loud' for a minute to see if I can make some sense out of my thoughts

there are so many great ideas, and I agree that as a group we should start nailing some things down so we can be ready for shopping, etc., by early September or else the cruise will slip up on us and we'll all be frantic (LOL).
T-shirts -- love the idea and we're interested! No designers here, but I've heard great things about using cafepress.
Gifts -- we've done gifts a couple of different ways on previous cruises -- one where everyone brought their trinkets to the 1st day meet that was prior to the safety drill, and another where folks dropped things off in fish extenders throughout the cruise. Some folks put names on the things they had so if someone didn't make it to the meet-and-greet, they could drop it off later; others just had enough for everyone and just had everyone pick up something. When there are 30+ DIS families, it gets a little hectic, and for some folks, it's just easier to make a hallway run and drop stuff off

Also if you have a delay in getting your luggage in your cabin, you might not have your gift for the first day meet-and-greet.
Fish Extender exchange -- some folks prefer to drop stuff off for fellow DISers in their fish extenders, but not everyone brings a fish extender. FWIW, you don't have to have a fancy fish extender; on our last cruise, we all had fabric tote bags that we hung outside that were fine for our new friends to drop stuff off. Some folks made one drop while others dropped stuff daily and others just a couple of times. We did this instead of doing a gift exchange at the meet-and-greet on the first day because our meet-and-greet was outside on Deck 9. Another things about the Fish Extenders is that as a giver, you might have something that you want to give on a particular day - like formal night or pirate night - so that would be the day you choose to make the hallway run
Secret Santa - I love this idea, but for the one who coordinates it, don't tell us if you do the "draw two names and you have each other" thing because it might be fun to leave surprises all week with hints or clues about your DIS identity and then reveal yourself at the end

If you have someone, then you'd know they have you - see what I mean? Of course you can do it that way - just don't tell us
Ornaments - it might be that the ornaments are incorporated into the other "exchange" options. I can just see us having so many things that we spend the whole time on the ship dropping stuff off

Good thing I will have the boys to do some drops for me (hee hee).
Meet-and-greets:
In the terminal -- absolutely agree that this is a great time to get together for those who are arriving prior to boarding time! We've met DISers in the terminal prior to sailing both times from Port Canaveral and we met DISers (yep, Lissa, that's you and your family) in the airport prior to our overseas cruise and each time that enhanced our pre-cruise experience!
On the first day -- just from our experience, I think an indoor meet-and-greet in a not-quite-so-busy but not out of the way location works well. indoors in case of inclement weather and to allow for plenty of space without interfering with other guests, not out of the way so that first-time-cruisers can find it without getting lost, and plenty of seating options for those who might need / want it. We've found that the Promenade Lounge on Deck 3 mid-ship (towards aft) has been a good location. We've gone to one on Deck 9 near the pools, but there was so much loudness from the music and comings and goings that it was difficult to do more than say "hey" and we were a small group (just four families).
During the week -- sea days would be a great time to have a meet time ... as it gets closer, we can check navigators to see what time might be good.
DS just walked in so I have to stop posting... still a secret.