Some girls in the Japanese school I study in are planing to do a Maid Cafe, which my teacher have sent me a message inviting me to take part into saying 「メイド喫茶に参加してみませんか？」. Honestly, I don't think I'm fit for the role, so I thought in a polite way to refusing him. I have thought about many different phrases, and now I think phrases like 「んん、私はそのような事があまり得意じゃないから、それはちょっと…。すみません。」or「んん、私はそのような事があまり得意じゃないから、それはちょっと無理です。すみません。」would be appropriate. I plan sending the first one, but I would like to know if using 無理 is unpolite and which other ways would be better to refuse an offer and recognize the other's efforts. I have seen people using 「気持ちはうれしいけど…」, but it seems way too personal to me.
I know he is my teacher and all, but the first semester has already ended and he won't be my teacher anymore next semester, so I would like to write properly.