Hmmmm, former hippie and former biker - are some of or all of the people you are inviting to share your day of the same genre? If so, maybe a retro theme back to the 60's - everything, music, wouldn't need much for decorations - the biker's bikes and lots of wild flowers would probably do the trick, lots of fresh raw veggies, brown rice, salads and for the bikers roast a whole pig in a pit in the ground. Forget cooking, if you live in the desert who wants to cook in that heat? As for drinks, there are lots of good "virgin" drink mixes of the regular drinks, google them by their regular name and put the word virgin either at the beginning or at the end. I know there's a Mai Tai one that is super good - I used to have the receipt. Also, don't forget the cake! Either that or stick with a desert theme and colors. If you're more comfortable in jeans and t's go for it. Remember, it's your day, do whatever your heart wants to do and enjoy yourselves. Congrats!