No way, not rude at all! DF and I are considering something similar, we're getting married next year and it will be a very small, low key affair. We won't be asking for gifts, but if people want to get a gift we'll be letting people know a small cash gift would be appreciated but is definately not the only option, to go towards our honeymoon. Some people think this is tacky but tbh it's our wedding, we don't want gifts at all as we have all the material things we need. We'll be having a small ceremony, and a small reception where we'll provide some food. I think it's okay to expect people to buy their own drinks, especially at a smaller wedding.