Paid carer's leave at a university: how many days, and do you ask for evidence?

I look after benefits at a Canadian university with about 6,000 academic and professional staff. A staff survey found 23% have regular caring responsibilities for an adult, usually a parent, and the unions have put paid carer's leave on the table for the next round.

We are thinking of five paid days a year, separate from sick leave and from the statutory family leaves, usable in half days. The open questions are whether five is meaningful and whether to ask for any proof of the caring relationship.

If you have a scheme like this, what does usage look like and did you regret the evidence rules you chose?