how to tell someone you're not interested after one date?

ok, so i'm a 19 year old college student working at publix (a chain grocery store). this regular customer comes in a lot and he finally asked to go on a date with me. he is really cute, tall, nice, funny, and in the military. however, he has been in the military for 10 years... meaning he is 28 years old. BUT he doesnt even look 28!! my guess was that we was at most 25.

to me, the age difference is a little wierd. he knew i was 19 before he asked me out and i knew he was 28 also.

i gave him a chance and we went to see spiderman last night at the movies. he didnt initiate anything and was really repectful the entire night. however, the age difference is still a little too much for me to handle at this point in my life. i dont want to start something with someone on an entirely different life path.

we've been texting and i kind of want to break the news that i'm not interested via text. but, i think it will make it super awkward when i see him shopping at publix....... how do i let him know i dont want to date him??? via text or in person? i'm also a little shy/timid/awkward and i HATE letting people down/rejecting them