我家在饭馆的右边 is not accepted. 家 is one of those words which doesn't need a 的 (like 妈妈，爸爸)
But is that only in the case where you're saying "My family"? Maybe 的 is needed when you're trying to make 家 represent an object/home, and you can only exclude it when referring to people.
I put exactly the right sentence, and it said I was wrong... The answer in the error message matches what I put...
sigh nevermind. I put 左 instead of 在