Adults should always try to protect children. It is our responsibility. You are right to be looking out for your grandchildren. You are also right to question if you are reacting appropriately. When a person has experienced abuse it does color their perspective. It is not always wrong for a father to kiss his daugher's on the lips, it is not always right either. The important thing in this example is if the children are being forced to do it or seem to not want to do it. Is it violating a boundary? If you observe this happening again when you visit, you should talk to your daughter and son-in-law about your discomfort. Explain how you feel more protective towards your grandchildren because of the abuse you experienced. The three of you should be able to talk about it, if you can't, that tells you something. Maybe you do have more reasons to be concerned.