In particular, you can use your voice. You can do this in a number of ways:
1) Talk to family and friends. People still don't talk enough about climate change in social settings, which can lead to a bit of a "circle of silence" as everyone assumes that nobody else is thinking about it since nobody is talking about it, so it must not be important. You can break that silence with family and friends, not in a preachy way, but in a way that expresses your concern and asks others about their thoughts.
2) Post on social media. These days most of us are our own 'broadcasters' since we can put stuff out on our social media channels. So, post about climate change. Join our Facebook page and follow our Instagram account and share things from there or from other similar places. (And, if you run into climate deniers, check this out).
3) Write letters to the editor. A LOT of people read the letters to the editor section in the newspaper. So, consider writing some on climate change. You don't need to be an expert. Keep them short and sweet. Express your concern as a parent or grandparent and call on elected officials to do more.
4) Write/call/visit your elected officials. The more that politicians hear directly from their constituents on an issue, the more likely it is they will act on it. A personal letter to an elected official counts for a lot, a phone call even more, and an in-person visit the most. Again, you don't need to be an expert - just speak up as a parent or grandparent and ask for more action.