We made the mistake of making a big deal about saving around $150 for each child (they were 7 and 10) and not having a game plan of how they could spend it. We couldn't go into any shop without a hassle. My son (10) couldn't focus his attention elsewhere...he just HAD to spend that money.
It didn't ruin our trip...but it did make it frustrating because they had saved so hard for their first trip and they couldn't understand why we wouldn't let them buy everything. Plus they couldn't foresee the hassle of carrying everything for the rest of the day.
This time we are stopping at an outlet BEFORE even setting foot in Disney. They get to choose one "big" thing and that is it. I will be happy to purchase edible treats...but the gift shops in Disney will be for browsing ONLY!
Good luck and have lots of fun!