To be honest, I'm in a similar position when my birthday rolls around each year. I don't have a lot in the way of people I'm close to, but generally my sister and I will go out bowling, mini-putting, or something along those lines. I'm not suggesting these types of things are necessarily for you, but perhaps you could think of something you would enjoy doing with your mom.
You mentioned that your entire family isn't one to go out and do things together. But is this something YOU would like? If so, maybe that could be the birthday gift you ask for.
It's perfectly fine not to know what to ask for as a birthday present. I think many of us are in that situation during holidays and birthdays ("So, what do you want for <Insert holiday here>?" "Uh ... I don't know.").
In any event, I do hope you enjoy your day and think of something fun to do
