Gifts over a certain amount ARE taxable, I think the amount is $13,000
However that can easily be strteched. Each Parent can give one child $13,000 for a total of $26,000 and the Parent can give the In-Law child also $13,000 x 2 for basically a total of $52,000
Also the parents can give the grandchildren money as well
Also money given to other sources like Yeshiva tution doesnt count, It has to be direct cash.
However some things are non cash income like if a Yeshiva gives a tuition discount in Lie of income, that can be taxable under certain circumstances