As a parent you will be in control. If you decide to have the baby, your child would definitely want to know their grandparents.
If they shun you, then you know the answer, if they accept the child, the you also know the answer.
As a 22 y.o. you are an adult and can handle this. The time will come when you will be thankful every day that you made that decision.
If you abort, it ends. If you go around seeking advice, especially from the grandparents and then decide to abort then you're affecting their lives too. In that case it does not end, the loss lives on in them. This is your decision, I don't think it's right to expose them to the anguish of telling them and then aborting.