Guy with an Instagram here...
Personally, I would have no interest in splitting my account--I want people to connect with ME, not necessarily just the work I make. Sometimes I post my kidlit stuff, sometimes I post a Batman sketch, sometimes I post a dapper Victorian dude holding an axe. I just make and post. And frankly, they all get a ton of love.
I dont just want someone to buy my children's book...I want them to buy prints or pins or tag publishers if they think I'm a fit for project or see when I announce an appearance. If all of those things are spread out of over multiple accounts, at somepoint you are going to cross post because you want to announce something and then dilute your brand anyway.
If it helps you mentally separate things, go for it. If your stuff is wildly different and your scared about your brand, sure...go nuts. It may totally work and rock. I think Instagrams are built over years not days. Just post. Dont overthink things too much.