Best way for children and grandparents to work together?

[Gerald Amasol]

Hi all, weird question time.  My in-laws are retired and are cash rich but can't qualify for loans because they are on fixed incomes.  Conversely, my son and daughter are working and have qualifying incomes but no down payment.  Grandpa and grandma want to help them to start investing but I was wondering if anyone had an opinion on them partnering up instead so that my children would be able to start their investing journeys while my in-laws would be able to show passive income that could help them possibly invest their money in other rental properties on their own?  I'm just trying to figure out a way to get both sides to help build up their portfolios and would appreciate any input!