Almost no Japanese people strictly remember which is a jōyō-kanji and which is not. Many hyōgai kanji are used by native speakers without even realizing it's so (e.g., 絆, 飴, 雫...). Of course, the police won't care, either.
Newspapers tend to follow the rule of not using hyōgai-kanji relatively strictly, but even newspaper publishers have their own lists of exceptional characters that are hyōgai but usable in articles.
That said, the spelling of takoyaki seen on signboards, Wikipedia articles and such is almost always たこ焼き (and rarely タコ焼き). If you used 蛸焼き, it would look simply unfamiliar, and some people might even wonder if you're selling something unusual.