Wow, that is one way to entertain myself as my kids play with playdough so...
1. No, I would not leave my children overnight to get a tattoo BUT I also wouldn't think less of someone who made the decision to do it just because their kid had a cold? That's all it was right? I don't leave my kids, pretty much ever. My 5 1/2 year old just started preschool, she is gone from me 6 hours a week. But that doesn't mean I'm right and someone who chooses to drop their kids off at the grandparents every weekend is wrong.
2. You talk about what awful people your inlaws are and then later on you talk about depriving your child of a relationship with her grandparents. If they are that awful do you really want your child to have a relationship with them? Family or not I get to choose who my children are exposed to and if there is a family member who is not a good influence then my kids don't see them.
3. Yes, 3 year olds hit. Sometimes they hit and have never been exposed to it. My 3 1/2 year old hits. My 5 year old has never hit anybody, EVER. My 3 1/2 year old has never seen hitting never had anyone hit her. It was completely off her radar until she started hitting. She hits because she's 3 1/2 and sometimes that's just what they do.
4. I am cringing at the idea of putting a 2 year old in a rigorous "school" just because a 2 year old CAN do it doesn't mean they SHOULD be doing it. It is not developmentally appropriate for any 2 year old. At 2 she should be singing songs, playing in the dirt, learning through exploring. And really $30K? The best colleges in my state don't cost $30K a year.