I love Helen C's response - great! Here are some thoughts.
Maybe you could come up with the budget. Make sure you discuss this with your husband. He needs to be aware of the situation and on board with helping you deal with it. If he is not, you will come out looking like the bad guy. If he is not on board with the budget and wants you to blow it out, just cut the corners you can and do your best because nothing you do is probably going to do anything but make you the bad guy. If he is and you set a budget, initiate a conversation with those "helping", especially your bride to be. Tell her you want to do something very nice, so you want to know what is most important to her to make her day special. Prioritize with her - she will need to learn it someday. Be nice, but make sure you let her know you are topping out and don't want to cut on the day (for the food and the necessary special things) or things that mean alot to her. That way she will reign in the others given that she is a decent mannered woman. Just be confident in how special you want it to be, but also NOT apologetic. Be sure not to talk too much, let her respond alot so you get her tempurature for later. Remember how neurotic brides can be!
Also, as far a the day goes, you could do chicken salad sandwiches (it is not expensive to make in bulk really - use lots of grapes and celery, makes it yummy and less chicken) on crossiants (not any more expensive, but tend to dress it up). Don't buy soda's or individual drinks. Make sweet tea and lemonade and coffee. Serve in glass punch glasses or if you have crystal and china - pull it out and make use of those beauties. Do not buy paper if you can help it, that is a huge expense and does not have the same effect.
Flowers can be picked and if you don't have left over vases or canning jars, borrow or garage sale them. Ask everyone you know for the table clothes (we all have 1 or two formal ones). Hopefully the season will enable you to pick some (big ones like magnolias or gardenias are great).
Be sure you offer the bride game choices. That way they will be fun for her and the rest.
Best I have, good luck to you. J.