You don't sound overprotective, I have two young boys and believe me, technique will be emphasized.
I do not recommend going heavy at the expense of technique by any means. What I meant is as heavy as he can manage with perfect technique and still trying to accelerate the bar.
James 1:16-17 ESV
Do not be deceived, my beloved brothers. Every good gift and every perfect gift is from above, coming down from the Father of lights
With God's help...Mens sana in corpore sano