Sorry--no. You are kind and generous and must be great grandparents. But only the person who can claim those children as dependents on a tax return can enter anything about the tuition or education credit on a tax return. You are giving that tuition, room and board, etc as gifts. And the cars are gifts. Gifts given to family members are not deductible on a tax return.
Gifts given to family members, friends or other individuals are not deductible. Gifts received are not taxable to the person who received the gift, and are not entered on a tax return.
If your gift exceeds the yearly limit ($18,000 per individual) imposed by the gift tax rules, then you will need to complete a Form 709 gift tax form and send it to the IRS, although it is very unlikely that you will owe any tax.
TurboTax does not support Form 709. It is not an income tax form and would not be included as part of an income tax return.
Here is a link to the form:
https://www.irs.gov/pub/irs-pdf/f709.pdf
https://turbotax.intuit.com/tax-tips/estates/the-gift-tax-made-simple/L5tGWVC8N
**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.**