Having a birthday! Please help for 5 star rating!!!?

[Sugar]

so, I am bad at planning social events. My 20th birthday was monday. A girlfriend texted me if I wanted to hang out (Mexican Restaurant) with her and another girl this saturday. She also said if i wanted to arrange it on facebook (note this!) I was excited and I said yes, but I thought she meant if I wanted to have a get together for my birthday this saturday, and to create a facebook event. so, I invited (my Indian friends 2 girls). Btw, my girlfriend and her friends which i know coming are 3 and they are all devoted Christians that pray before they eat e.t.c. I realize this gathering will be awkward for my one indian friend (Hindu). So I am thinking that to make everyone less focused on the other, Should I invite my muslim guyfriend from ethiopia, and also 3 guys and 1 girl (my close Nigerian friends-- I had a dinner with them on Monday).
We all go to the same University and I feel they could discuss classes e.t.c They are all chill people!

-Do you think this is a gathering for disaster, and I should just go with the 3 white girls who are Christians and cancel on my Indian friends?
-Do you think I should just bring these two groups (All girls, white and Indian)?
-Do you think I should invite everyone I mentioned so they know I am not racist against my own race (black, Nigerian)? Also, there will be less attention towards anyone cos there will be 12 of us?

I really don't want to offend the girl that gave me the idea- Should I let her know others are coming?

Also, Note there are only 4 black guys invited for 3 different races of girls- Should i be worried?

Lastly, I am a pretty awkward person to meet and introduce people, how do I make them socialize with one another when its only a dinner??

Should I cancel restaurant, and make us go to a food and game type of place? Am i overthinking?