The Society for Creative Anachronism is one option, but you'd have to find someone willing to teach youngsters about heavy weapons combat.

There are other heavy weapons martial artist organizations out there. Jill Bearup (on YouTube) is a stage combat person, but she's also had contact with people who do martial arts in the space.

Of course, if you want to learn Japanese style sword combat, go down to your local Kendo Dojo.

For people wanting to have a bit of fun and handle things that feel like weapons, I'd highly recommend searching out a contemporary Wushu (Kung Fu) school. It's the modern sport martial art of China, is sort of a combination of traditional Chinese Martial Arts, Kickboxing, and Gymnastics and weapons are a very big component. It's very close to becoming an Olympic sport even though it's not incredibly well known.

For reference, it's what movie actor Jet Li was trained in and performed when he came to the White House in the 70s as part of the U.S.-China opening up.

Ex-gf of mine did HEMA (https://www.hemaalliance.com/) for a bit. Gear isn't cheap, but it seemed fairly serious and welcomed all skill levels.