OK, so I kept the niece and nephew again but by myself this time and it was...interesting.
I've realized (and communicated) that crying doesn't bother me or make me change my mind or make me yell or anything else. You can cry to your heart's content. Good luck with that.
But we worked on offering your seat to a lady, honesty, tattling, whining, crying when we can't have our way, actions having consequences, sharing and holding hands when crossing the street.
Mr. SLS was able to check in once during a break in his day and we talked about what I learned from the day this morning as he was packing for his annual two week military adventure.
All in all, it was a decent experience that showed me what my skills -- and limitations -- might be as a mom.