Last year I was in such a bad state I didn't want a birthday party. I was so angry at everyone, especially my friends, two of which ignored me until I demanded to know what was up and I spent my birthday and Christmas (four days apart) feeling sad and depressed because of it. I didn't get too many birthday wishes.
I'm sorry people forgot your birthday. I'd be crushed. I say go for the guy. As long as you're a legal adult, there's really no shame or wrong in dating an older man.