No problem investing in student housing for children, this is commonly done.

I believe you can ask them to move even with rent control in place IF the new owner or a directly family member (Spouse, Mother, Father, Children) want to move into the unit.

I got ownership of a property (I got the deed and agreed to pay the seller a mortgage) and opened it to women with children in need of housing.

I only had the oppty to meet and speak with one of the prospective tenants, so before running the credt/background checks, I 'invited' the prospective to bring the other tenants (children) to view the house and that we wanted to meet them.

This may be married couples, live-in couples or parents with adult children. 

Perfect for my children.

Which is a bit odd because I don't even have any children (yet). 

His wife passed away in 2015, leaving her half of the ownership to her four children.

The problem with your particular case would be the marketability when trying to promote it as "great for your adult children" or "let your parents live in the in-law suite" - however you phrase your rental ads, this would violate Fair Housing rules that prohibit discrimination based on familial status.

Kudos to you for saving for your children's education.