Such history is often as the Arrogant worms say in the introduction to their Gaelic Song "passed down from father to son, from mother to daughter, from uncle to goat."

In all seriousness I would think that the formality of such a thing is dictated by a couple of other factors. First how formal is your family in other things? It should be representative of who you are not who you are not. Secondly how large is this collection? If it is large, you probably don't want to take the time to describe each item and tell a story about it, but perhaps reserve that treatment for a few outstanding pieces. Third, how large a gathering will this be, and will it be part of another event? A large ceremony at a small event will almost always seem out of place. However even at a large event if this is just one part, it should not be so large as to take away from the main activity.