I'm seeing a real puzzle facing those who want to write about H/L kid(s): How do you involve parts of Disney-canon that might work, or are at least palatable, without involving parts that don't work, or aren't palatable? Despite what the wording here may imply, this isn't about what is "allowed" and what isn't. Rather, it's about what sorts of approaches seem agreeable and workable. And, importantly, this isn't about further lamenting what TFA screwed up. Instead, it's about what to do with the pieces; how, and in what ways, do we move forward?
Examples include....: Would we have a story that involves Poe growing up with Jaina and Jacen? If we have a story with Poe, do we just make up a new name for H/L's kid? How do we handle gender? And of course, if the new kid isn't "Ben," then who is s/he? Do we need to spend a paragraph or two of character development on our new character, Han-and-Leia's-kid-who-is-fine-and-not-Ben Organa-Solo?
Of course, I know this is ultimately up to the individual author... but still, it raises interesting questions about how to then present and share the work with others, as seems to happen a lot in fanfic ;)