What kind of proof do y'all required for 2 yrs & younger to get in free?

I've never had a problem with this. You just tell them.

I didn't have to show evidence as a member.

You just tell them your kid is 2 or under

Just in my personal experience they haven't asked me I just told him my son's and daughter are younger than two which was true went the time I went but like I said this is just personal experience