Of course lots of kids get over stimulated at this time of the year, but there's a difference between behavior problems caused by excitement, stress, and fatigue and those caused by ADHD.
When our hyperactive kids were young we discovered that caffeine had the opposite effect on them compared to how other people react. I read information about the disorder confirming that reaction to be frequent in kids who have the condition. However once people with ADHD reach puberty they tend to react to caffeine in the usual way.
After the holiday excitement is over, things have calmed down, and your family is back to eating as usual. you might want to try giving your kid a lot of chocolate and see what happens. If the child becomes over stimulated he or she is reacting normally. (Obviously it's best not to try this before school or bedtime.)
But if the child becomes sedated after eating the chocolate chances are good that he (more boys than girls have the condition) has ADHD. If that happens please check with your medical practitioner and ask your local school district for an evaluation. Many districts will do tests for free even for children who are not yet of school age because early intervention can make a difference.