Whenever I live in a predominantly Muslim country, people (friends, neighbours) invite me countless times to eat at their home during the Eid (Aïd) week. It's a major religious holiday for Muslims, and unlike the Ramadan, it's a very sympathetic and joyful one -unless you're a sheep of course!-.
Yet, I make no mystery of my religious opinions, (almost) all my friends know it. But they still continue to invite me, and we share a good time together, and that's all that matters. Nobody told me that my presence was a disgrace in the face of Allah. And nobody tried to convert me either.
And it's quite the same with the Couscous in North Africa every friday. Fridays are supposed to be the day of the jumu'ah, the day of worship, and thus you have special traditions and eating habits. And even when you're not Muslim, well... you eat Couscous every friday.
It doesn't seem to create any problem at all. Why should it?