I haven't finished reading through this whole thread, but want to put my 2 cents in. My sister and I used to sneak out to go to meeting etc because my parents weren't JW's. I am afraid that if you verbally say something to your wife about not taking the kids out in service, the elders will encourage her to go behind your back because you will be viewed as an opposer. And the kids may get the idea that it's kind of fun and cool to do secret JW things that Daddy doesn't know about.
My advice to you is to be subtle and sly. Plan fun activities for the kids those days--maybe not every single Thursday but 2 or 3 out of the month when possible. If your wife complains, you might say that you don't mind her taking the kids out in service once in a while but that you want them to have some summer fun too. Is summer school an option? Also--spend some "Daddy" time with your kids away from your wife as much as possible, so they can get to know that their "worldly" dad is not such a bad guy. And talk, talk, talk to your kids--let them know whatever doubts you have about "God's Organization" and let them know things you have learned about WT scandals and cover-ups as they mature--but let them know that those issues upset their mother. Build a strong relationship with them when they are young, don't wait until they are rebellious teenagers!
I wish you much luck for a very difficult situation.