In my opinion (which might be wrong) your duty as a parent is to equip your kid with the tools it needs to be able to face the challenges life throws at him/her.
What would make your kid _happy_ would be to play all day and do nothing about their future (I'm yet to see a kid who would rather study than play).
Wanting your kid to be _happy_ means you need to prepare him/her to be _successful_ (aka to be able to face the challenges life throws at him/her) which might not be _fun_ in the short term. As the OP mentions, striking a balance is a tricky part.
What would make your kid _happy_ would be to play all day and do nothing about their future (I'm yet to see a kid who would rather study than play).
Wanting your kid to be _happy_ means you need to prepare him/her to be _successful_ (aka to be able to face the challenges life throws at him/her) which might not be _fun_ in the short term. As the OP mentions, striking a balance is a tricky part.