Shrink Me Please!

So I have some new neighbors. They are fabulous, wonderfully kind people. They have my son's best buddy. The boys play and have a great time together. My son went to their house yesterday to play. I told my new friend that I needed to run to a neighboring town to pick up my daughters cake. Would he be ok there while I went. Sure she says, actually I need to run into town also can I come with? Sure I said great!
And then it happened. The girls got home from school, I told them what we were going to do. I warned them there would be someone coming with us. They saw her walk into our home. And yet.....still trouble ensued. "I need a snack" one says. "Bring it with you" I say. "Actually what if we went a little farther to this other store" I say. "Then I'll stay home and I'm not going" she says. "Fine forget it we won't go there" I say. We finally get into the car and get on our way. Meanwhile one arguement after another. Get there..."can we buy this?" "can we buy that?" "sure we can use that." Time to go. Get into the car to drive to get cake and go home. Get Cake and start voyage home. Fight ensues. "She's kicking me" "She looked at me" "Why are you sitting together anyway?" "Sit on your hand and cross your legs" "look out of opposite windows" They are twelve and ten. Meanwhile the new neighbor friend is holding the cake hoping for the ride to end. Did I mention they were psych majors? Shrink me please!