For example, one of the major battles of the Revolutionary War was fought on my [several-]great-grandfather's farm grounds.
Without sounding like I'm gloating when talking about the event, how can I get folks outside my family excited about the event, my ancestors' role(s), and become engaged with contributing to my personal research / family history projects?
You'll have to change your point of view.
Genealogists and family historians are not interested in "Your Ancestors". They are interested in "Their Ancestors".
When you can, always give them the story from their point of view. When you talk to them, refer to people as "your great-uncle", "your ancestral home town", "your family". Don't include anything that will not be connected to them in some way.
Then you won't sound like you're gloating. You'll sound like you're interested in them, and they'll be interested in adding what they know.
In this case, you say these are folks outside your family. Then you really are in a bit of trouble. Truly, few will be interested.
What you must do instead, is not try to present your material to genealogists or family historians. To be brutally honest, we are only interested in history in general if there is some connection to the family we are researching.
You could present your material to a Historical Society. Those people are truly interested in history in general. Many of them would be interested in the Revolutionary War and would be glad to hear your personal story about your grandfather's role in it.
If you present your stories to historians with an emphasis on the history that unfolded around your ancestors, they'll be interested and you won't sound like you're gloating.
Blog. Write about interesting family history events; relate the events to things readers find interesting. Spice it up by writing some about "finds" and proof and a brick wall here or there, but write too about interesting historical events. The TV series, "Who do you think you are?" was so successful. For some, the most interesting part was not the quest for the record, but gaining a better appreciation of the events that impacted on their ancestors' lives. Broadening the story makes things more interesting to more people.
Covet thy family photographs. Folks really seem to love the old pictures. Gather as many as you can, document them. If you have the resources, publish these in a wonderful book for the family. To the extent you are able, add a little written color to the images with historical or family factoids. You can add public domain graphics and art work. This same content can be used as filler articles on your blog, from time to time.
Target your audience/market your material. If you blog about something that might be of interest to a local society, don't hesitate to send them a link to the blog. Welcome their critique and/or review.
Ask them about their Family History. I've sat down with people, brought out my laptop or smartphone and started doing research with them. Nothing say's that we can't go right in and show them something they have never seen. I've related with strangers that have had questions on the spot. People aren't usually interested in another family's historic documentation, they are however intrigued by another family's stories.
I would tell the story. That it was your ancestor may not matter as much to others as it does to you, but if the story is compelling, that will get attention. It might also be useful to give the broader historical context and then bring in the details from your research that give a more personal account of events. Media such as maps (both of the time and contemporary) might make it easier to understand what happened.
Find a medium that they're comfortable with and publish stories (and photos when possible) through that. It may be email, a blog, or an annual newsletter in the mail (heaven forbid). Then ask people if they have any stories that they would like to share.
Contributing stories they already know and photos they already have is the limit for most people. Getting them excited enough to research is much more difficult. Many people just don't want to be genealogists.
It's been my experience that people are interested when they understand how something might be related to them. I would present the information in a way that brings the listeners' family into the picture.
For example, "I was doing this research on the Revolutionary War and discovered that one of the Battles was fought on my 7th great grandfather's farm. Do you know when your relatives arrived in this area? I wonder if your relatives knew my relatives? Have you ever heard any stories in your family about this Battle?"
If you are interested in someone else, they'll be interested in you.
