Hi Rose!
Way to be preparing for your financial future! Sometimes I hear from from babies who are twice your age and haven’t even begun to think about these questions. You are on the ball!
Well, congrats to your parents. They’re killing it. You’re a lucky baby to have such good role models.
Regarding the $150/month. Let’s work it out. The current cost of a 4-year in-state tuition is around $22,000/year, including tuition, fees, and room and board. That means putting a kid through college today will cost about $88,000. Ouch! Let’s round it up to $100,000 for good measure.
You’re about 0 today. $150/month for 18 years at a 7% rate of return comes out to about $63,000. That means starting your freshman year, your parents will have to pony up about $770/month (instead of the $150) to cover the difference for the next four years. That’s not terrible! And maybe you’ll even have a scholarship or something that will cover that, so you won’t want all that extra money in a 529.
7% is a reasonable inflation-adjusted growth projection. But it’s also possible/likely that tuition increases faster than inflation. So that might be a reason to want to put away a little more too.
But either way, I’d say it’s a pretty darn good start!
Regarding getting a baby job so you can have a baby Roth IRA… I don’t know. I suspect that the IRS will have a problem with that, but that might be a better question for a CPA or an estate planner.
But broad strokes you’re following the two rules and killing it! Keep it up! 
