My safe tips are probably the same as most:be prepared for any weather so your not having to use up your time and money buying stuff at the parks. I trained in the cold and the cold during the race was not even noticeable, but the two hours of sitting in the wind and cold waiting for the start zapped me of tons of energy. It was miserable. If you have the option, get the race retreat.
Also, I like to take time to really relax before the marathon, like enjoying the resort. For me, when I was a kid, we could never afford to stay on property, so I love using the time to mull around, swim, eat, etc...
Also, I probably wouldn’t sweat worrying about merchandise disappearing at the expo on the first day. It can happen, but most of the time you will find it there the next day.