One particular difficulty (I am now realizing) in running PbP games with kids... is demonstrated in this exchange of dialog with Gnomsky at the Hero Shack. Getting our kids to play off of the dialog that has come before can be difficult. It's much easier to ignore someone's suggestion when they aren't right in front of you. Roxin's suggestion to all chip in was a good one, but my daughter didn't care about that suggestion because she knew she wanted the purple stuff.
In Real Life, she would have, at the very least, acknowledged the suggestion with a "No" or "That's a good idea, but..." or something. Anyway, it's now on my mind with her to help coach her through the dialog, making sure she understands that even though this is a very asynchronous method for playing, the events are happening back-to-back in Storia.
Inevitably, all of our kids are going to make suggestions to the group, and those may go ignored. So, helping them understand the role of dialog, and the back and forth or give and take of communication is critical to making people feel included, etc.
I'm not suggesting we start coaching them on what to say, just voicing my awareness of something I hadn't anticipated, because it doesn't happen (at least not the same way) in face-to-face games/interactions. I will try and be aware of the impact that my NPCs have on the group when entering in to discussion too... to try and be more intentional about constructing conversations.
Food for thought.