SunLass plays volleyball on her high school varsity team (she’s a rising senior) and a club team. I expect different sports have different ideal times for starting learning the sport - soccer, for example, takes a long time to learn the muscle memory needed to develop the leg and foot skills to play the sport at a high level, and the ease of learning the sport at even the youngest ages means there is a lot of expectation to start very early.
For volleyball, I would tend to question whether anything done before middle school is of significant value. So much of the sport - and all of how you specialize for a position - is based largely on height, and while you can project some from looking at parents it’s not an exact science. From middle school on, though, learning basic skills, positional play, a team system, and the like are going to be more easily taught in a club context than at their school team.
SunLass’s club is large and does a lot of developmental work at all levels. The travel teams are made up of the best players at each level and they get extra practices and tournament time. She has players on her school team at both travel and region levels, so while it’s certainly a bonus to play travel ball it’s not an absolute necessity.
You mentioned clubs demanding parental extreme dedication. SunLass’s club actually tends to discourage parental overinvolvement - we sign the checks, show up, root, and that’s about it. Many clubs get the parents a little more involved, but we find that her club gives the athletes a little more self-reliance, and frankly many of those clubs have parents that are, shall we say, not the best exemplars of sportsmanship.
Two things you should concern yourself with as a parent are burnout and overcoaching. SunLass decided herself she wanted to try volleyball, and once she liked it we haven’t needed to push her at it - she’s very self-motivated. We do emphasize to her that she can take a break from the sport if she needs one, and that it’s most important for her to take care of herself. She’s played club for four years now, and burnout hasn’t been a problem - but teammates, for one reason or another, will sometimes get the point where they’re hating a sport they used to love.
Players sometimes end up overcoached when they simply aren’t suited, talent- and body-wise, for the sport they’re playing. Their coach has been able to give them all the skills but they’ve hit their top and they’re not going to get any better. This can sometimes be frustrating for parents who see their kids passed in the pecking order by kids who may not have the same level of skill, but have a higher ceiling on their talent.
One thing you might want to consider, especially early on, is allowing your kids to rotate between sports rather than overspecialize at an early age. Might not help in the long run if your goal is a college scholarship or pro career for your young’uns, but I suspect it would be better for having sane kids.
I’ll close with an anecdote. The summer before she started high school, SunLass did a volleyball camp at the local university. She got to play against an all-Pac-12 middle blocker and heard her volleyball experience - which started as a high school sophomore. Again, a huge chunk of her advantage as a player was innate talent and height, which can’t be coached - but her lack of long-term experience with the sport didn’t keep her from going a long way as a player.