Heya,
I feel your pain, I'm always working with kids. Tough stuff. I too do it with a Rovelight often. But more and more I'm just ganging up speedlites.
A few things I've learned just doing lots of young kids (the kind that do not take direction/commands or hold still, etc):
1. Having an assistant to manage the light source is a huge help. I still do it often by myself, which is super hard. But when I do have an assistant, wow, it helps so much.
2. Proximity to child is a big deal, they clam up if you're up in their face with big modifiers and a camera clicking away. I often go long for this reason.
3. Prediction of where they will go, and what they will do is a big deal. Talk to the parent(s) to get an idea of how they tend to behave.
4. Over-exposing skin and dropping it in post is a good way to go, angel skin.
5. Parents never select photos based on technical aspects, they just look for what connects them to the child, so it may be the blurry photo with the weird facial expression. Don't worry about it!
Unless I'm shooting in bright sun, I leave the Rovelight out. I use the Rovelight for knocking out the sun purposes or extremely long range with a big modifier as "omnidirectional fill" in a way. I find that speedlites are so much easier with kids. You can set up a few and face them in a few directions and just hang out on the perimeter and let the kid play, zoom the speedlite and just generally face them towards where they're playing and capture with telephoto waiting for facial expressions. I do bursts of faces to capture small micro-expressions. I also like speedlites because the kids never, ever stay where you want them to, and moving the Rovelight takes effort. When I'm doing this in the Florida heat, it's a physical chore that gets very tiresome! A bare speedlite on a stand weighs nothing, and can quickly be placed and moved. Again, I like to have lots of options. More and more, I shoot natural light when I can when it comes to kids that are hard and I just make sure to over-expose and drop in post later for the bright smooth skin.
As for prediction, I know it's a tall order, but getting to know some of their common habits helps you to be in the right place for the behavior. For example, if the kid does something and often looks to a specific parent, you can place the parent so that the kid will look that way and be some where to capture that look. That's the kind of stuff I meant. For small children, I use this with the parent. A fun example I use with 2 year olds, is the parent spins around with the kid or does something fun that the kid likes, then puts them down and have them jog a direction that you want the child to then go, while still cackling and smiling, and have yourself in a place where your light and your lens are waiting for them to cross into your path chasing the parent. Again, just predictive stuff like that helps you line up shots with uncooperative kids. Little kids always want their parent so being far away and using the parent to guide the child where you want them and guide where they look, will give you more opportunities!
Very best,
