So I did it. I 'came out' to my mom, who will tell my dad.
For a icebreaker of the topic it went surprisingly well. I didn't get to everything and certainly not more of the 'scarier' traits of SPD but I think she gets at least a basic idea of what I'm going through.
Though she did fall into the common trap of "Depression? Oh everyone gets sad sometimes, just cheer up!" (But reworded to fit SPD) I pointed it out to her and she seemed rather ashamed.
Other than that though she seems like she'll try to be supportive (though how long that will last as I get more into what SPD is has yet to be seen.) but it seems things may turn out well.
My dad is very INTJ (or at least something similar to it) as it is so he'll get over it pretty fast, or at least be able to relate more.
I'm still thinking over my mom's reaction though; I think it'll be hard for her to wrap her head around. She's a very feely person and my lack of emotion is very foreign to her. (As well as my very brief description of depersonalization; where she really has no clue what I was talking about)
It's a long road ahead I'm sure but for a start things went better than I thought they would.