My sister and her FI are having a true elopement (well, planned elopement whatever that is called) and NO ONE except her 4 year old daughter will be there

Moms on both sides, mainly his, would like to have an AHR. My sister and her FI are on board with the idea, as long as they can do it their way. My sister is an outdoor party, bring the kids, come one, come all kind of a gal. She has a lot of people she wants to invite, but not a huge budget. So far, she has ideas to have a local creole/cajun restaurant cater and has music sorted out. She doesn't plan on doing anything traditional except maybe the "first" dance. She hasn't made cuts on the GL yet, but is dreading it. I was trying to come up with ways to help her cut back so she could make room for her guests and need to run one by you. Since it's just a picnic, does she need to serve cake or cupcakes? I voted no, and I'm someone who loves sweets. Our mom gasped when I suggested that. I just figure when I'm outside at a bbq/picnic, I'm not put out if there isn't any cake. It's not a formal wedding reception, just a big casual celebration with food and some dancing.
Was I wrong to suggest that? Any other ideas?