Well, I am not one of the layout gurus, but...

I think putting chairs/seating directly behind the sink/DW is a really bad idea. And that aisle looks to be 36"? Even worse. There is no way there is room for a person at the sink while someone else is at the table. And maybe you think it will never happen, but isn't the point of having the table in the kitchen so people will sit there and hang out while you work in the kitchen?

I also think the end of it that you label prep is pretty small to do much but make a salad. My main prep space is 42" and it's plenty long enough, but it has a wall at the back of the counter so if I push something to the back, I don't have to worry about it falling off onto a table below. Additionally, that prep area is no where close to a water source, so if someone is standing there prepping and needs the water, they have to trek over to the sink, then trek back dribbling water everywhere.

I guess the removing the wall question depends on how you see yourself using it in the future. Do you prefer to eat in the kitchen? Do you only do it b/c you've set the DR up as a playroom? Once the kids don't need playroom anymore will you begin to eat there? You need to plan the space for future use and not just focus on the immediate use.

if you open up the wall, would you want to keep the range in the peninsula? and do you have some thoughts on where you would like the double ovens?

i agree with KathyNY76. generating a short list of your personal reasons for wanting to open up the wall would be useful. it also may help others here offer other options to attain your goals.

i'm assuming that long counter between your sink and range is your primary prep space...