(B.S. in Psychology, 21, diagnosed with ADHD, medicated since 5th grade,very knowledgeable about ADHD)
Hi, I know that behaviors of young children can manifest in a way that seems like it could be ADHD, but a reason why your doctors are probably hesitant to medicate your child is because they are smart and know what they are doing. Its just too early in development to do so.
I recommend reading the Diagnostic and Statistical Manual for Mental Disorders for clinical criteria. It states that these symptoms need to be having a dramatic negative effect on more than two different settings( home, school etc...)
In my experience, and many others with ADHD, my ADHD has impacted my acedemic ability the most. I think a reason your doctors are waiting is to see if your child's symptoms cross over into the school setting and are negatively effecting his performance. Since he is not old enough to have "grades" yet, just wait it out, I dont know what you're going through, but medicating a child that young is not something anyone wants to do, and should only be done in very rare instances.
I would recommend being slow to get angry at your child for being forgetful or getting distracted. Trying to decrease that behavior by getting angry will not work.
Give one task at a time, and use praise and reward systems for following requests immediately and for good behavior. Good Luck