@bomerr just keeps giving terrible advice about starting a smattering of unrelated activities. And doubles down every time someone challenges it as wrong headed. OP, do the ECs you are interested in. Spend more time on the volunteer activities you have already started. Don’t worry about the person you work with recording your time, no one goes back to ask. Just make an honest assessment of what you have already spent and go from there.
In addition to adding some more volunteer time at the things you have already been doing, can you be a referee or work with a youth league in some way in one of your sports?
Don’t sweat the leadership thing too much. One of my kids got into U of Chicago, Swarthmore, Harvey Mudd, and Carleton with no leadership (no team captain, no club offices, nothing). She was a really strong individual performer in one of her activities (had a team and individual component), though. When asked about leadership in a college essay, she was able to talk about being a leader by example. Your mentoring volunteer work is a kind of leadership, too. Leaders aren’t all standing in front of the room with a title. They are working hard to help their organizations succeed, motivating others who are working alongside them, and sometimes quietly influencing in the background.
And do NOT worry about diversifying. If you had just one activity, I would say you should branch out a bit. But you have a couple of sports and some volunteer time. You are fine, just keep doing what you are doing.