I have to agree with what everyone else is saying. If you are having all of those people come down to Mexico with you, you might as well bite the bullet and pay a little extra for the life long memories. Otherwise why not just have gone on a honeymoon alone?
What about doing your reception in the buffet restaurant? Or forego the cocktail hour and appetizers that come with the ultimate package and see if you can negotiate the 20 people paid for in the cocktail hour for another 5-10 dinners in its place.
We also have 40 coming down and I have to admit the extra charges for exceeding the package is really adding up. Good luck negotiating the wedding reception that you want (with FI and Dreams)