I bought what I thought were comfortable sandals for my trip to Disneyland last summer. I was on my feet most days from 7 AM until about 1 or 2 AM. By the second day, my feet were killing, and by the third day, they actually swelled up!

My right one was noticeably larger than my left. I noticed this while standing in the tiny, hot, crowded laundry room of the Tropicana about midnight. There was no place to sit, and I was trying to eat a very late dinner/snack from McDonald's while waiting for a dryer to free up.
I bought Crocs because everyone here, and at home, raves about them. I bought the kind with that movable strap on them. They are big on me, because I have tiny feet. But as long as they are comfortable for a crazy, busy mom of three, I will be happy.