Besides breaking the 10 commandments, what else should we strive to not do on Sundays?
Or instead, what should we do on Sundays? 

Nor should we do something that requires another person to work. 

So, if getting to Mass and back entails the purchase of gas, food, drink, or use of public transportation, one should stay home?  For a variety of reasons, I can no longer get to Mass, however, when I was still able to drive long distance, was it sinful of me to purchase a tank of gas to return home?  Travelling with 10 gallons of pre-purchased gasoline in a tiny car hardly seems safe.  Is it wrong to sign in or leave a motel on Sunday?  After all, the maid needs to clean the room!  What about eating in a restaurant, fast food place, or purchasing food at the gas station convenience store?  What about using a restroom in such places?  Menial work must be done by someone to clean and replenish supplies, even if no purchase is made.  Before EZ Pass, tollbooth collectors sat their shifts and my passage required them to work. It was not possible for me to get to and from Mass toll-free.  
I know I'm being trivial, but where, exactly, does one draw the line?  Once, I was rebuked by a woman for sewing on Sunday, and was strongly urged to go again to Confession.  My sin?  Retrieving a sewing kit from my car to assist my friend who had caught her dress on the corner of a bathroom stall door, ripping the dress along the waistline about seven inches, then all the way to the bottom hem.  Was she to stay in the church bathroom until she could sneak out after midnight without being seen, then drive home?  What if someone saw her while walking from the parking lot to her apartment building?  She didn't have extra clothes or a long coat.  I thought I had performed an act of mercy!  Maybe not!

So, if getting to Mass and back entails...

The operative word is, "unnecessary".  You should go to Mass and do what you have to do to go.  Furthermore, when it comes to restaurants, someone has to prepare a meal; so whether you prepare a meal or the people at a restaurant, it is necessary work.

What you shouldn't be doing is you weekly grocery shopping and things of that sort.

If you have a specific issue under a specific circuмstance that you really question is necessary, you should not do so until you've spoken with your confessor.

When I need to get something from the store, I use those self-checkout lanes to minimize the amount of labor I am causing someone to do.  And I get gas by paying at the pump.

I know I'm being trivial, but where, exactly, does one draw the line?

I've seen moral theologians who say that doing 2 hours of unnecessary menial labor constitutes a mortal sin.  These theologians feel the need to draw lines.  While they seem arbitrary (what if I do 1 hour and 59 minutes?) ... it's helpful to have rules of thumb like this.  Doing a small task would be a venial sin ... unless there's sufficient (relatively light) justification.  Doing a lot of work requires a more serious justification.  Acts of charity are no sin and require no justification ... if they're really pure acts of charity and are necessary.  So, for instance, I can't spend 3 hours working in my neighbor's yard just to be nice ... but I can do it if I'm helping out some elderly person who can't do it otherwise and I have no other time to do this, provided that the risk of scandal is avoided.

I always liked motzoh ball soup, potato knishes and beef brisket....this would be a nice task for a Sunday Jєω and a Sunday meal, but maybe that's a little meshugena

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Anyone who applies for work at Home Depot is informed that they have to work Sundays. An applicant who wants Sundays off is told they're being moved to the bottom of the list where they probably won't be hired.
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Home Depot doesn't hide the fact that it was started by and is run by Jєωs.
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I think a lot of "service industries are like that now.  Oh for the good old days when 7Eleven was the only store open on Sunday. When I was growing up I remember one gas station being open and that was out on the highway to mostly service long distance travelers. Now grocery stores are even open on Christmas Day !  We have truly lost any sense of the sacred.

Speaking of Home Depot and the Jєωs -- well, there's no surprise here: Home Depot pledges to continue support for gαy agenda despite massive petition/boycott

My husband calls it Homo Depo.