It’s wonderful that your son and daughter in law want you involved with your new grandchild.
I think it’s best to wait until after the baby is born and the mother has had time to adjust to being a new mother. It is not unusual for a new mother to get very possessive and protective once the birth has taken place. It’s best not to make work plans until mother has had adequate time being a new mom. It’s something one has to experience to understand.

It has been proven that mother child bonding is a very important part of healthy development in a baby. It’s NOW recognized through a great deal of study that early bonding is very important so this is not just my personal opinion.

The best way to handle this is to respond with showing respect for the mother and that you would rather move slowly based on her comfort level. Men don’t understand this, it’s not anything they experience first hand.

Allow her to have the say and proceed very carefully and gradually. If the wife is happy your son will be happy 😉