I'd do a passed Margarita or a agua fresca since its in mexico. Some traditional things you can look up I'm not sure if your having a religous ceramony is a lasso ceramony and arras ceramony you can search for both online. I'd also try to keep the food more ethnic someone gave you ideas for spanish as in spain but I'd go for more traditional mexican. Id think succulants and sunflowers for flowers and go for colors like cobolt and yellow. I think if you do some google searches you'll come up with great ideas. Good luck