It depends on their ages. Sometimes toddler & pre-school behavior can have the same symptoms as ADHD. At this age, unless the symptoms are severe, then it's normal. For older, school age children it depends on whether the symptoms are severe enough to interfere with their success in school. Your best bet would be to talk to your children's pediatrician & have them evaluated to make sure they are correctly diagnosed as having ADHD or just exhibiting normal behaviors.
My son has ADHD, his symptoms were classic, & he was diagnosed by his pediatrician but I did a lot of research & tried every study habit, work station environment tips as well as working along side his teachers using other tips to try to help him focus before we decided to use medication. Once the medication was started, the difference was night & day & the positive changes he made at school made it obvious he needed the medication to stay focused so he could succeed to the best of his ability in school.
Not every child with ADHD needs medication & I don't give it to my son during weekends or when he is on vacation but he definitely needs it to succeed in school. I encourage you to do a lot of research, try every non-medication route to help your children succeed if you feel they do in fact have ADHD & work closely, & often, with your pediatrician & all adults involved in the care of your child & make an informed decision regarding whether they are ADHD or not.
Good luck :)