Got my first dev job interview soon and the company want to take me out for dinner, is this normal practice?

A lot of places do it. It is more relaxed than sitting in an office, but remember it's still an interview! be yourself, but be your professional self.

I'm more concerned with finishing a meal without spilling it over
myself (a task I normally do really well) than I am about the interview.

@CDESmith If you do, you'll probably fit right in! :-p

They probably just want to know if you're a person that fits their company culture. Are you sociable, how well do you communicate ideas and concepts, etc. Don't stress, instead enjoy the meal :)

Yeah to free food!

Taste your food before you season it. Yes, you are being watched. Manners, proper etiquette, always drink alcohol slower than the interviewers. Order healthy food like fish or salad and water w lemon. Don't go for the most expensive item, do t order from the barely have enough to pay section. Order food that is appropriate for your age. Don't get the dinosaur nuggets and apple sauce from the kids menu... Yeah, someone did that.... Have fun.

@jagalbraith best advice ever XD

in my native language (Hindi) there is a saying Eat the fruit why count trees ?