I'm starting the girls on HERO, and have stressed the role play part from the start.
My experience is the kids are naturals! My seven year old has surprised us with excellent one liners, including "I'm gonna make you eat dirt!" Normally she is to shy to deliver a good speech, but she loves the one liners. her cousin otoh digs making presence attacks and giving speechy speeches.
Jessica already has a well developed sense of morality, but it took a few tricks to drive the lesson home to Bianca. Her PC has a ranged killing attack (electrocution), a NND no range eb (shocking grasp) and a normal eb (lightning bolt). In our first encounter, she electrocuted a normal, killing him. I had the deceased child run out to her prone daddy crying, and when the police came they took her away because whe no longer had a parent to care for her. This made Bianca very thoughtful, and now she doesnt want to use her RKA (um, even when she should lol).
BTW, the crazed AK toting normal was under mind control by The Wizzard to create a diversion. Bianca PC, Electric Girl, is not a member of the gang but just a friend of The Shadow. It wasn't until our last adventure the girls learned The Wizzard has mental powers (that do not affect pre puberty/children, not that they know that either).
Both girls like slipping into their secret ID's and going out after dark, slipping out the house and doing what the wnt to, wheich has been a little silly at times. In their secret ID's they are treated like adults, which they really like. As Jess said, "I could stay The Shadow forever."
Be ready for some amazing, and wild, and even, well, dumb, ideas. Electric Girl has desolid with linked flight that allows her to travel through electrical systems. When they first came to the jewel, it was inside a secure case with alarms. She wanted to enter her hand though a light, desolid just her arm, reach into the case via one of the display lights, and grab the jewel. It was freaking brilliant. We moded her desolid power to have 2" stretching on the spot and I demanded an EGO roll at -4. She rolled a 1, 1, 2! They got the gem, the elementals appear (I asked B what she did when they appeared and she delighted me by responding I DROP THE DIAMOND!) and we stopped for the night there.
Jessica had the idea that Biancas PC could follow her by riding in the cars electrical system. I asked for a roll to see if Electric Girl could hold her form without blowing out the cars fuses, and she failed the roll by one, so when the car was half weay to its destination, I had the car break down.
My point is the kids have had some really neat ideas. They have kept me on my toes and really dig into what I put before them. I recommend lots of NPC's to make the world seem real. Don't let them live in a vacuum. be sure to stress the imact of their actions. When The Shadows full power 12d6 shadow bolt missed the villian, it tore a gapeing hole in the museum wall, I was sure to describe the damage done to the exibit, and I'll go back to it when the news covers the story and talks about the finacial cost and loss of Native America artifacts (and I have a native american villian that will be showing up when i need him to kick her bottom...I want the first meet to be very direct. I can bring him back later). I encourage good ideas, but I want them also focusing on their responsibilities as heros, not acting like this is a video game.