Hi Laura!
Many guests enjoy being on a Disney Dining Plan. Some guests save a lot of money by being on a plan, some guests save only a little bit, and some guests actually spend more money by being on a plan. Unfortunately, I can't tell you what would be best for your party because I don't know what you like to eat, where, and how often. However, I can offer some advice.
You can get more information on the various Disney Dining Plans
here. I suggest looking at the menus for various Table Service and Quick Service restaurants at Walt Disney World. In my opinion, the best place to find menus is at AllEars.Net. The team at All Ears does a great job keeping their menus up to date. You can price out what your party would order, throw in a few extra dollars for snacks and drinks during the day, and then compare that to the cost of a Dining Plan.
Whatever you do, be sure to make an Advanced Dining Reservation (ADR) for any Table Service restaurant you are interested in. ADRs can be made up to 180 days in advance and many Walt Disney World restaurants book up very quickly.
Enjoy planning and write back if you have any more questions!