I haven't tried this myself yet, but I watched a JW video in the summer festival that touched on it. Bad Red Head Media, I think it was by.
They suggested for MG, parents are still choosing the books, so it's them you need to target, but by YA, it's the teenagers themselves who do the choosing, so focus on them. You're kind of in the middle so maybe have to think about both.
It was suggested you use social media to funnel readers to your email list. So for tweens you'd focus on Instagram (I think that's the most popular with them) and parents, wherever they hang out.
Will be interested to know what you decide and how it goes.