Reminded me of your situation: http://www.morethantwo.com/polycatlove.html
Regarding the relationship with your husband's parents, I've learned from experience that if you act ashamed, people will react as if you have something to be ashamed of. If you act as if you still care about them and are just in a tough place, that's a different story. Maybe write them an email and tell them that things are crazy right now, so you may need to have some space and not come over, but that you value your relationship with them.
Me, 30ish bi female, been doing solo poly for roughly 5 years. Gia, Clay, and Pike, my partners. Davis, ex/friend/"it's complicated." Eric, Gia's husband. Bee, Gia and Eric's toddler.