While I’m certainly not an expert, I wouldn’t start worrying about ADHD just yet, at least until the assessment’s done. Behaviour that is noisy, impulsive and emotional is developmentally normal for 2.5 year olds. Doctors know this, and I would be surprised if someone would be willing to diagnose ADHD in a toddler. More likely they will suggest some different strategies for you to try in managing his behaviour. It’s also important to remember that kids have different temperaments and some are more highstrung and reactive than others; it doesn’t necessarily mean something is wrong.