Dollar Store Dilemma

As a reward for good behavior this week I decided to treat my kids to a visit to the dollar store.  When they were younger this was almost a weekly occurrence but as they've gotten old and gotten more "stuff" we've cut down on going.  We all know most of the toys there are cheaply made and break rather quickly (anywhere from minutes to weeks usually). I knew that they would thoroughly enjoy going and it would help cement the idea that listening and doing what you're told will pay off in unexpected ways. 
The kids were thrilled to hear I was taking them.  They even bypassed on the idea of going home to change out of their pajamas (it was pajama day at school).  I made it clear right up front why I was taking them and the fact that they could pick any one thing.  One thing and one thing only.
I have to say my son was understanding of the rules.  He promptly thanked me for the treat and never begged to buy more than one item.  My daughter only had to be warned once.  My reply was this, "If you ask again you will get nothing so don't ask.".  She knew I meant it so that was the end of the never ending begging that sometimes occurs when I'm out at the store with them.
My daughter is fairly adapt at going through the store and figuring out what she wants.  She will pick a few choices, debate them and then chose.  And that is that.  She use to waffle more but has really amazed me the last year in being able to do this.  My son however, will continue to change his mind and it drives me crazy.  He will walk around the store 5, 10, 20 times picking things up and discarding them.  Over and over and over again.  I start to slowly lose my mind and my patience.  I now have to give him a time limit or this can go on for over 30 minutes and he starts to annoy himself with his indecision. 
Today it was between a few different things.  A cash tray with money, a paddle ball, a foam fling type toy, bakugun type toy or a kite.  Back and forth, back and forth.  He continued to narrow it down.  At first the kite wasn't in the running because he didn't see it hidden in its display by an endcap. It was down to the cash tray and the bakugun type toy.  He asked me to put them behind my back, shuffle them around and then he'd pick a hand.  He picked left and it was the cash tray.  This was the first thing he was drawn to anyways so it worked for me.  He's learning how to subtract dollars and cents in school and he thought this would be a fun way to help him learn.  I'm all for that considering he "hates" to "learn".  His words, not mine.
Then he saw the kites right before we made it to the check out.  Dang!  So close, yet so far!  He picked 2 out and we went through the motions of me putting them behind my back and him picking a hand again.  It was a go again.  Until...  I let him know that we could only fly it at the nearby park because our yard is too small.  That put him into a tizzy.  After settling down we came to an agreement he came up with an I can live with.  We got the cash tray today and if he's good all next week we'll go back and get the kite.  Hopefully by then the weather will be a warmer since it's been in the 20's all this week.
In the end everything worked out.  I think these excursions teach kids about making (appropriate) choices.  It also includes logic, problem solving and decision making.  They're definitely learning things without even realizing it.