You can set up a situation in which you observe the way a parent interacts with a kid. They way they talk with the child, the way they play together are all incredibly important for good language development and can be an indicator for how the parent will be interacting with their child at home once they're born.

Even having classes where future parents learn about how to raise their child in a good way would be a good start. Make it mandatory and not something you choose to do. Chances are that parents who do partake in such classes aren't the parents that need to be taught about it in the first place.

Point is, there's plenty things you can and should offer - everything's better than having nothing of that sort right now.