What if I don't want professional hair and make up?

I never wear make up except for special occasions. I don't like the look of fake eyelashes and caked on make up. I am wanting a fairly simple hair style and natural looking makeup for my wedding. I have 2 sisters with some good quality hair straighteners/curlers/etc and intend to get some good quality make up, do trial runs and keep things fairly simple but also nicely done. We have always done each other hair & makeup at previous weddings we have been to. But is this wise? What are the downsides of DIYing our hair and makeup?