Nice weekend project -- How often you are sending data to Elasticsearch and how does Kibana is polling the Elastic?
Another good combination would be Influxdb + chronograf
Another good combination would be Influxdb + chronograf
Grafana is more mature and Chronograf is closed-source, I don't see any reason to go with it.
But yes if you want to display time series there are better options than Kibana, which has a focus on searchable documents.
I'm not entirely sold on the idea, as their examples for turning metrics into actionable insights are a lot more complex than they are for Grafana (or similar).