I like Snooze2978's suggestion. The only thing I would do a little different is
(Mom's name and Dad's name) joined (date of marriage)
We added (baby's name and date of birth)
This Makes Our Family Whole (or something like that)
Then underneath
this was lovingly made for "baby's name" on (date) by "Mimi" with pieces of
the dress worn on the date this all began