Trip to Costco

After school on Friday, the kids and I went to Costco to eat lunch and then do grocery shopping. We've done this a few times now where we order pizza and get drinks, then eat, and then shop. Grant was being a really sweet boy that day and he was being sweet to Kate. At one point he held onto her arm like this:

It was so cute that I had to snap a picture. Later I tried to get another picture of them both smiling and looking at me but this is all I got:

Kate saying "Nooooo" and Grant saying "Cheeeeessseeeee". Usually it's the other way around with Grant being the stinker and Kate being the sweet one, but lately from Kate we hear a lot of "Noooooo." "No." "No-no." "no." - all with a smile on her face, thinking she is hot stuff. It's great when she tells me no to something she doesn't want as an option or to tell Grant to stop when he is doing something he shouldn't but when she tells me no to something I am telling her to do, that's a little different. I know this is a stage (and a stage Grant didn't go through at that age so in some ways it's a first for us even though she is our 2nd kid) but I desire for her to have an obedient heart and to foster that at a young age. I am finding that it is hard to get her to understand that she can say no to me (or Grant) sometimes and sometimes she is to say yes and obey. How do you get a cute 2 year old girl to understand this???