it is admirable that you want to participate in your grandchilds life.
There is no guarantee that mom will ever cooperate with any court order. Orders are barely enforceable as a parent in the same state. Sadly, even though a traffic sign says “stop” does not mean everyone will obey the law to stop at the sign.
Rather than gifts or lawyers fees, set up a savings account with you as the trustee on his behalf at your local bank (or stocks) Don’t tell the mom, dad or child about it. Instead of birthdays or Christmas gifts, Put the money (as little as it may be) into the savings, or stocks for his college or his future. Later, you can always change your mind.
Consider keeping a journal of letters you will one day give your grandchild. Remember, his mother is depriving him of a relationship with you too. Mazybe stories of when your son (the dad) was littel. Boys want to know more about their heritage when they hit their teen years. So worse come to worse, wait. Even if it never happens, your son may re-marry.?!?
THis is not legal advise. It is based on the fiscal & emotional school of hard knocks. It is easy to say, hard to do.