Late in the day I was asked if my child would be available to help with the next event at the extracurricular activity mentioned above. This event takes place three hours from here on a weekend during which all but me and this particular child have prior commitments. My SIL says, "I got roped into serving a dinner for 40 and I could use all the help I can get." (Notice though, she asked to invite my child, not me. Apparently she forgot to add "....except for you, lkb") I said I would have to check our calendar to be sure.
You know what I noticed? She didn't ask if your kid would like to enjoy the activity.
She asked if your kid could work at this activity.
Don't lose sight of that. That's not an invitation. Your child wasn't invited.
Your child was recruited. (Well, OK, not successfully--but that's what that was. A recruitment attempt. Not an invitation.)
This. So much this.
This situation reminds me of a memorable telephone conversation in which I was involved when I was about 13 or so, and beginning to go through the confirmation classes and such at the church my family attended. That was also the age at which you were invited to join the youth group at the church.
So, I was at home one day, minding my own business, when the phone rang. Mom answered the phone, and then said it was for me. So I said "hello," only to hear in response (no "hello," no "this is X,") "You have to come and help at the Youth Group soup and sandwich lunch on Sunday."
I reflexively replied "No, I don't." (Seriously, there was almost no conscious thought involved...it was out before I knew I was going to say it.)
"Well, why not?"
"Because I'm not in Youth Group. Bye now." ::click::
They never tried to voluntell me for anything, ever again. I also didn't go to the Youth Group events. Considering that most of those involved in Youth Group had bullied me pretty mercilessly most of the way through elementary school, I didn't consider it much of a loss. Mom was a little upset with me for not being more polite about it, but she did understand.
(Basically, we lived in the country, more or less between two towns. I went to school in one, but we went to church in the other. So most of the kids who went to that church went to school in that town, so I was very much the outsider, and very much treated as such.)
Good for you for not making your child do this for the sake of "family." Much better for him to have a fun, memorable day with you.