Is it risky to have a non-academic, non-native English speaker as a letter writer?

[BakedPotatoSoup]

I have been out of school for 2 years, and am currently teaching English in Japan. I'm planning on applying to graduate school (Social Psych PhD) this year. When I was in college, I was a shy girl at a big school that didn't learn how to build connections with professors. After graduation I volunteered in two labs under two PhDs for a year and figured it out (These will be my first two letter writers). Now, I work with two Japanese teachers of English relatively closely, and they both are very complementary of my work ethic. I am unsure of asking either of them however, because 1) They are not connected to academia or my field and 2) both only have a decent command of English. I don't think admissions would be very kind if they received a letter full of grammar errors and awkwardly worded sentences. I'm strongly considering having the one I choose write their letter in Japanese and have it translated (I know a guy), but I'm not sure how it would be submitted.

I'm sure it would be ideal to find a professor from undergrad, but at best I would get a "she was in my class and got an A" letter. These teachers are the ones that can speak most accurately about my current work ethic, but may or may not be able to connect it to research. Should I still pursue this as an option, or should I try to reconnect with a professor from undergrad and start building a relationship and ask them?

Edited April 26, 2016 by BakedPotatoSoup
minor correction

[fuzzylogician]

The non-native speaker part of this is solvable, I think. For example, by having the letter translated and then returned to the writers for inspection and submission. What worries me more is that these sound like peer-evaluations, not a letter from a supervisor. It's ok to have one letter from industry and two academic ones, but you'd want the industry letter to be from someone who is actually in a position to evaluate your work. A supervisor sees different things than a peer. A peer wouldn't know about your job performance, complaints, or successes, outside of what you tell them. They can perhaps talk about observing you in class, if the teaching environment allowed for that, but beyond that not much. Can they credibly talk about your students' performance in examinations, beyond what they heard as part of office gossip (=do they have access to official results)? Are they in a position to compare you to others who've had this job in the past? And more importantly, is anything they can say relevant to the degree you are pursuing? If not, this is not much different than a Did Well In Class letter, except that depending on the content, this letter may say that you did well in things that are even less relevant than the potential DWIC letter.