Of all the five cats I have owned so far none had ever had hairball
problems.
I would only treat for that if it became a problem. That's sometimes when
the cat is older or has long hair.

Carola

I have three felines and only one has hairball problems. She kept
hacking and dry coughing in a manner several times a day and never
seemed able to get them up.

I give her just a bit of a remedy every couple of days.
I would wait before using it on kittens.
See if they have problems first.
One thing that helps is if you are consistant about brushing too. And
since yours are kittens its a good time to get them comfortable with
brushing and clippin claws

This is a great time to start brushing them. My Ragdoll comes running
for the brush and if you know what a Ragdoll looks like, you can
imagine how often I brush him. I'd get a brush with boar hair bristles
on one side and metal ones on the other, each kitten may have a
preference. I'd also suggest using Iam's Hairball treatment dry food.
I mix it half and half with the low activity food for my cat and it
really helps. Save the Laxatone for when they start coughing, my cat
HATES the taste of it so be warned, your kitten may fling it off
his/her paw. Good Luck!