Ideas, please

Hi! I'm looking for ideas for decor for a scarlet red, navy blue and white wedding color scheme. It's a church wedding, reception venue undecided, but possibly in the church fellowship hall. Guest list about 75 people. Will be a casual reception. We are considering a BBQ with hamburgers, hot dogs, both with the works available. Also potato salad, baked beans, and maybe chips. We are going to serve assorted soft drinks, lemonade, and water. (No alcohol). We are an "older" couple, so the reception won't go on for more than 3 or so hours. I'm looking forward to any and all ideas anyone would have to share. Thanks! P,SI know this screams July 4th, and we're ok with that.