Roundout, what type will you be in, and will you have anyone else in the front seat?
I suggest you do a weight+balance check - some designers assume that if you've got less than 4 people in their 4-place aircraft, you'll have two people in the front. You may find that, with two in the back and only one in the front, you're out of the centre of gravity limits, in which case put some luggage or ballast up front. Make sure you secure it properly, so that it can't slide forward and get in the way of the rudder pedals.
That's apart from any considerations about your son, of course.
FFF
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