Advice please. Engaged at 16?

I have been with my 19 year old boyfriend for a year and three months, and he proposed to me at my leavers prom. I get on with his parents and he gets on with mine. I know people may think that we are too young to be engaged or know what 'love' is, but that is your opinion and only I can know how I feel. We are just trying to think of a way to tell our parents, and wondering how they'd react to it. We aren't planning on getting married until we're at least eighteen. Advice please? :)