Congratulations on your success!
If you choose to provide individual monetary awards, my suggestion is that you NOT incorporate them into your celebration lunch. Make the awards to each individual, in private, in the days following the lunch (or near the end of the year, or at the time of their next annual appraisal).
When everyone on the team is getting the SAME cash award, it's okay to make it a part of a celebration event. When you are highlighting individual contributions with recipients getting different amounts, however, that's not the best forum. No matter how carefully you handle it, the people receiving (and not receiving) awards will share, compare, snipe, and gossip. Each individual will question his or her perceived value to you and to the organization. The whole thing may have precisely the opposite effect you intend -- people (even ones who receive awards) may leave the celebration feeling cheated, hurt, or resentful. The average performers (who did their job, and did nothing wrong) will feel particularly left out and taken advantage of, and you don't want that -- we NEED the average performers in order to succeed, too.
A great way to recognize those individual contributions is to prepare a "story" of your project, complete with PowerPoint slides, and present it at the lunch. Every successful project has its "moments of truth" where the whole thing could have fallen apart if certain people hadn't risen to the challenge. Putting these "heros" on center stage and bragging about their accomplishments makes everyone feel good.
I have a project that will wrap in December, and for it, I am currently writing the "story" and having an artist prepare a "graphic novel" of it, complete with comic characters for each key team member. In our celebration, will show it in PowerPoint frame-by-frame with narration and dramatic music. Then everyone will get his or her own copy of the novel in booklet form, and we'll have an "autograph party" where everyone will be encouraged to write messages of thanks and congratulations in each others booklets. In my experience, the amount of attention and praise people receive is usually well in line with their contributions, so anyone feeling "left out" knows in their herats why they are (and they often make a better effort on the next project).
My "heros" WILL get a nice monetary bonus, too -- but I will meet with them one-on-one to deliver that.
Again, congratulations on your success and best wishes!