Nope.

You did right.
It will not be fair to either kids. Not fair to Lao da, being penalized to being older, not his fault. Not fair to Lao er either. He will be used to have the advantage of being younger. When he goes outside of family, he will be surprised that no one else will let him get his way becuz he is younger.
Kids need to fit into society, so how society plays, is how it plays at the house.