If the kids really are back with Nick and Kayla full-time, and Nick celebrates by taking his side whore out for the night while leaving their mother at home with the offspring he claims to love so much, I can only imagine how much that is fucking with the kids. Children are ALWAYS fiercely protective of their mother. And if their mother is unhappy, so are her kids.
It’s bad enough he moved April in to disrupt their family dynamics. Those kids are going to end up justifiably hating Nick’s guts if they don’t already.