Assuming there are two grandparents----they can each give up to $15K to their grandchild (or whoever) in one year without the need to fill out a form 709. If the grandchild is married, they could even give another $15K each to the grandchild's spouse without having to fill out a form 709. But if their gift exceeds that $15K per person, then the form 709 must be completed. They do not PAY gift tax unless someday they exceed a lifetime amount of over $11 million in gifts given.
If they gave the grand child over $30K they must complete a Form 709 even though no tax has to be paid with the form. And you have mentioned $100K more than once. That means they do have to fill out that gift form. They might need to seek paid tax help to complete the form---if they can afford to give a gift of $100K they can also afford competent tax help.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
