As a parent (and a parent of a five year old boy no less) I would much rather candid shots of him in his element than the sterile "say cheese" shots! I assure you they will be outstanding and the parents will love the comfortable enviornment you created than a forced smile session.
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.