When you're staying with family who has friends over for dinner but you're not joining: how best to handle?

I'd say avoid the disagreement with your mother by joining the dinner. You're not doing yourself a favor by avoiding people just because they're older and married. You'll have a greater chance of success in the world, not to mention fun, if you can get comfortable with all kinds of people as quickly as possible.

Sorry but I have to agree with #3....it really isn't a big deal to greet them and then say, "sorry I can't join you but I have errands etc...to run... I hope you all have a great time". I don't think that's rude...but then again I am probably your mom's age...lol...so us older folks will probably have the same opinion.

But whatever you decide...don't stress...

I would say 3, because if you know them and they are older than you, you should say "hello," and then go off and do what you want.

It would be fine to greet them all, spend 5 minutes or so, and then say (politely), "Excuse me, I'm on my way out. I hope you all have a nice time together."

(I'm probably your parent's age or older and that's how I raised my children who are 26, 29, and 31 to be respectful of their elders).

It doesn't really matter what you want to do, if your mother suggested 3, that's what goes.

Yes... mother is always correct in the world of etiquette!

Greet the guests and promptly excuse yourself...

"HI Matt and Gerri! So glad to see you! I hate to meet'n'run, but I have some irons in the fire that I need to attend to. So if you'd please excuse me, I need to make my rounds! Have a great dinner... it smells great!"

Have a polite day.

Etiquette takes over where laws end.

Ultimately, you need to do what feels right for you. If you are not comfortable in saying hello to your parents' guests, put your attention elsewhere. You might want to ask yourself why you do not want anyone to know you are at the house, are you embarrassed by this somehow? Why do you feel it rude to acknowledge guests as opposed to no interaction with them? Only you can know. Regardless, do what is right for you.

are you going to hide from them in order to keep them from knowing you're there? that seems rude to me. but, no need to feel bad about not joining them. you have previous plans. they'll understand. and i agree with mom on number three. plus, you'll want to at least say, "hi," right?

Choice number 3 is the most polite option in your list.

I vote for 3 too.

Just say to everyone that you have eaten and go to another room while they eat.

i think your mom is right, the 3rd one seems more polite