M.L.
Isn't it funny that folks with straight hair want curly hair, and those with curly hair want it straight? The grass is always greener....
I have wavy hair - which means it's neither fish nor fowl and doesn't do anything I want it to - but it gets wavier as it gets longer. When my boys were little, their hair curled if it was left long enough, but they usually liked it shorter and straighter.
Perhaps your husband's hair grew thicker as he grew older. That could affect the curliness of hair, too.
You could take a picture of your boy now to preserve all those curls in your memory (and in the scrapbook). Then take him to the barber shop and ask if they can cut his hair enough to make it manageable but still leave a little curl in. Enjoy the decision-making now, because when your boy is a little older he'll have opinions of his own!