Don't charge them. Building your portfolio, you should ask to use their pictures for your website and promotional work free of charge. Your friends will be pleased, hopefully they will tip you lunch money, and then spread your business word-of-mouth.
Your photos have a good quality, but you need more experience before you start charging. Your lighting is off, and the movement photo is blurry. I have shot two entire horse shows for free, plus many free photography sessions in exchange to use them for promotional work and practice. Do it for the love and money will come. :)