I've got 18 people for a very casual evening at the end of August. I've catered cheese enchiladas, rice and beans and Mexican rotisserie chicken. I'll have chips, salsa and guacamole. I'm going to make a large green salad. I'd like a couple of additional side dishes. I thought of corn salad with red onion and black beans, but it doesn't excite me. I'd appreciate any ideas for not-too-complicated things that I can make in quantity, preferably a day in advance. Thanks.