I decided to ask my sister about this because she and her husband are both doctors. She said it is up to the individual doctor when they will diagnose ADHD, if at all, since each doctor brings his or her own prejudices or beliefs into their practice of medicine. (Just like some gyn's will not prescribe birth control because it goes against their personal beliefs). There is no hard and fast rule about when it is appropriate to diagnose ADD or ADHD according to the AMA.
There are many doctors who are hesitant to dx children early with things like ADD, ADHD, PDD (Autism Spectrum) for many reasons. That speach delay might be apraxia instead of ASD. That hyper-disorganized behavior could be Sensory Processing Disorder or PDD rather than ADHD. And frankly, some of these behaviors are very overlapping and not always easy to tag. Thus the book:
"Kids in the Syndrome Mix of ADHD, LD, Asperger's, Tourette's, Bipolar, And More!: The One Stop Guide for Parents, Teachers, and Other Professionals"
That said, I think that the hesitancy to dx (b/c the dr. might be wrong or feel that he/she can't clearly identify a dx) doesn't mean that these kids don't have issues that are clearly identifiable at an early age. They do, but if they are not severe enough to get an ASD dx (and people don't evey like to give that dx until age 2) they will go un-dx'd for a while.
If your physician has diagnosed ADHD for your child, they should be providing you with techniques you can use for your unique situation (because each kid with ADHD has a variation in what will or won't set them off).
Maybe that's true and maybe in an ideal world that would happen. In my experience, if your lucky most peds. and dev. peds. will at best point you in the right direction or suggest some options, but you really need to figure most of this out on your own. (At least if you are looking for options other than meds...).
Finally, to the OP. I understand that at least one person suggested you are really dealing with what other parents of 3 yrs. old deal with. While I'm sure to some extent that is true (what 3 y.o. wants to wait in line), thinking of my own 2 children I have to acknowledge that it is different. My 2 y.o. is much better equipped to stand in line without loosing it, acting inappropriately or running off than my 4 y.o. (My 4 y.o. is not dx'd with ADD, but I believe he may be dx'd one day.). It can appear to be the same thing, but it's not, even if only as a result of the degree difficultly. Not so say that my 2yo can't give me heck...b/c it happens frequently....but it's just different. My 2yo tests and throws tantrums, but ultimately knows exactly what's going on and does not suffer from the distractions and impulsivity -- of course, I may have just jinx'd myself).
In any event, good luck. I hope you have a fabulous trip.