The kids will benefit simply as they are harry and Megan’s kids, famous parents, which will make them curiosities. Nepotism may still loom large in a couple of decades. Kids of famous folks, even the infamous like Harry and Megan have a curiousity factor, doors opened due to it. I think it’s less to do with the titles and more the fact that the titles will identify who they are immediately.
however it’s a long time till they are grown up, and a lot can happen between now and then. At the moment it looks impossible for the Sussex;s to make their way back, but if Harry is single, I’d bet good money he will come back with his tail between his legs, and that would mean the kids have some insight into the royals during any visits to the uk.
it’s also feasible if harry and Megan spend the next 5 years or however long, behaving themselves, doing charity work, even publicly reaching out to the royal family and saying some truths that are positive. Time is a great healer. Right now it’s too raw, too current. Too continuous.
the thing is it will need to happen in Charles’s life time.i think William will give him a roof over his head, an allowance, but no more. The children though make it more complex. But I don’t think there is a way back for Harry to William, and he will be king, likely by the time the kids are adults.