I'm thankful you're concerned about this; the time to think about this is now rather than later, after you might have unintentionally harmed your relationship.
I'm sure most of us have seen examples of mother-in-laws (and father-in-laws) who didn't get it right -- either interfering too much or else cutting themselves off almost completely from their married children. But neither extreme is wise. On one hand, the Bible reminds us that marriage brings with it changes in a couple's family relationships. In God's plan, it says, "A man will leave his father and mother and be united to his wife" (Matthew 19:5).
But this doesn't mean their parents are no longer concerned or should have no contact with them. I think, for example, of Naomi in the Old Testament. She clearly had a close and loving relationship with her daughter-in-law, Ruth, especially after Ruth's husband died. Ruth even declared, "Where you go I will go.... Your people will be my people and your God my God" (Ruth 1:16-17). As a result, Ruth became an ancestor of Jesus.
Ask God for wisdom -- and as you have opportunity, ask your son, as well. Seek advice from your friends also (although every family is different, and what's right for one may not be appropriate for another). In the meantime, invite them for dinner from time to time... share family news with them... gently offer to help in small ways. God has given you a great privilege; use it wisely.