Where can I take my nieces for horseback riding lessons?

I have two 9 year old nieces who have been really interested in horses the past few years so I wanted to see if I could get them into riding lessons. Does anyone know of a good place around Kansas City or the surrounding area that would be good to look into? I have a bit of a budget but understand that some of the lessons can get very expensive. I would just like for them to really get to experience something they seem to love so much.