How can a man help a random woman without making her feel unsafe?

It was a bit late and there was a storm rolling in. Me and a lady happened to park next to each other so I offered to load her groceries while she put her kids in the car. She almost said no until she realized I work there. But within my lifetime, that's definitely going to happen at places where I don't work. Other than not offering, is there a way I can let people know that I just want to help and don't mean any harm?