To begin, a party of over 8 people, regardless of whether the restaurant is empty or full, requires a wait time. The staff will have to determine where you can be seated, and most likely will have to move furniture, and determine which server can handle a party that size, in addition to any other tables they might have. A 20-30 minute wait is standard, not something to complain about.

MA Cunningham made a good point - a simple call ahead would have allowed them to have the table ready when you arrived - making the whole experience smoother for everyone. They would have known to have the table set up and the staff prepared. If the restaurant was mostly empty, they may have been short-staffed, and unprepared to handle a party that size.

And I have to say, I tend to think that the OP left much out of her story - as evidenced by large gaps, only noting what the staff "did wrong." Honestly, the fact that she didn't immediately apologize and agree to keep everyone calm when approached by management was a telling sign - she actually admitted that they weren't "being any louder than anyone else" there.

Maybe management was rude in their requests to have the kids keep it down, per the OP, their requests may have been poorly phrased. Regardless, I feel like we're missing part of the story, as the kids must have been making too much noise, and I'd almost guarantee her wait times were completely exaggerated.

If there are valid complaints in this letter, they're being obscured by the rest of it. Simply saying, the children may have been excited and hungry, but: A) management was rude in their requests to calm the children, and B) the wait time for food, which would have helped get the children under control was too great; would have made the letter much more succint, and easier to sympathize with.
_______________________________________________

And I think Mr Helpful made a good point - unfortunately, I've never seen a parent take it well when someone asked them to restrain their little ones - it implies bad parenting, and tends to put the parents on the defensive, so they immediately cry discrimination, when it's obviously not. Discrimination would have been refusing to serve your party - this was a simple case of trying to handle a difficult situation as best they could.