Sorry to hear about your grandfather. Hope you made it to wherever you needed to be on time.

Write United Customer Relations an e-mail succinctly explaining what was wrong (no more than one short paragraph per problem; no more than three problems in a message). State facts about how the company disserviced you. Add a note about how this made you feel and then explain what aspects of the service you would like them to improve in the future.

Expect to receive a form letter in two to six weeks; don't necessarily expect the response to indicate that the agent totally read your message, but expect at least a boilerplate "sorry you feel that way". You may also get a $75 electronic travel certificate, probably a high probability.

Depending on how much you value your time, you can also contact United Customer Relations by phone (the customer care department is 877-624-2660) and engage in basically the same process but by phone instead of by e-mail, possibly receiving a more empathetic response because it's harder to send form letters over the telephone.