Do you think your friends are using this as a veiled way to tell you they do not think your sandals look good enough to wear to dinner? Of course, we can't judge, as we don't know what your sandals look like. But, if they are Earth Shoe looking, maybe they figured it would be better to (white lie) tell you that restaurants don't allow sandals than to say "You are NOT going to wear THOSEEEEEEE sandals to dinner with us, for goodness sakes." ????
If you don't feel comfortable, take a pair or ballet flats from Target.....they pack like almost nothing and are a good basic shoe to wear just about anywhere. I wear them with jeans or to a very dressy event where I know it will be too dark (or crowded) for anyone to really inspect my shoes :)
Flat and comfortable is good for walking many blocks or just a block or two in Paris. But, for heavy-duty touring, I prefer my Merrells or Arcopedico sturdier shoes....the Arcopedicos might pass at a nice restaurant (age has its advantages ;) , but not the Merrells with Velco straps :o
Have fun, and let us know how you enjoy your special dinner.