I challenge the statement "I just want one photo of them all smiling looking at the camera." Do you? What if, perhaps, what you really want is what the smiling means. That what you are actually after is for you and/or your kids, to be happy. And excited. And full of wonder. And to have an image that reflects this. We think smiling means happy, but anyone who has seen a forced smile, or a cheesy grimace, has got to know that it really isn't the same thing.
I believe that one of my biggest jobs as a photographer is to "see" the people I am capturing images of. And that means seeing past the nerves, the falseness and the required smiles, and waiting for the real moments. The fun, the laughter, the joy. Whether posed or completely off the cuff doco style; the realness is the same, because there is truth in real moments.
What a grin. That is not a smile you can get from saying cheese!
Maybe you don't need a grin at all. Maybe you just need a memory. Looking back and realising that he couldn't stand to wear shoes...
And sometimes so many photos say so much - that I might be inspired to create something like this. Unique, but somehow You.