Parentcaster

Struggling to avoid frustration with family , particularly older relatives, when it comes to the kids. 

They do things out of laziness and selfishness that encourage bad habits or cause a problem later (like ruining naptime or something). 

They don’t listen and then they give me shit for having to be on their case.

Your house, your rules. 
When your are/were in their house, you respected that. They have to respect the same in yours. Their boomer ways don't work in how your raising your kids. Remind them of the countless other boomer things that don't work like lawn darts. So respect your rules or visit at a different time.