Thanks, everyone, for all your support and well wishes. This trip does not seem meant to be, but I am pressing on neretheless. Not only did my friend offer to come along and then back out, but then I found out that my mom was hospitalized so I went to NJ to see her last weekend (everything is better now), and THEN, yesterday morning, I fell down 2 steps and sprained my ankle!
After all that, I almost cancelled the trip, but I'm feeling better this morning and I am SO determined to carry out this crazy plan!
I now have a sling for my little guy and twin harnesses (leashes or reins for you British folks out there) so I can keep tabs on both kids while they stretch their legs. (Even at the age of 4, DD was once separated from me by pushy people in line at Pinnochio's Village Haus and it was a scary 7.5 seconds for BOTH of us -- the harness should prevent that from happening again) I've made name tags with instructions to "please take me to the Baby Care Center if you find me." Anything else I should do in this, the 11th hour?
I'm feeling as prepared as possible thanks to all the help from my friends on the DISBoards. Thank you all!