I've been to Nice twice & never found it overly expensive to eat out. Definitely cheaper than here in Belfast. The poor exchange rate will have a difference but I don't think it'll be too bad. Choose carefully: all menus are displayed outside so no unpleasant surprises.
There are many good restaurants in the old town around the Cours Saleya & also along the Rue Massinet ( the long pedestrian shopping street.........I think that's its name!)
One restaurant that we thought was excellent & good value was the Barracuda on Rue Mayerbeer near the Palais de la Mediteranee hotel, but you probably need to book.
Hope that's helpful. Nice is a fabulous city for a short or long break. There's so much to see in the surrounding area.
You'll have a great time....you lucky thing!

Thanks got back yesterday and guess what ate a the barracuda and was 1st class also found a sicillian restaurant just off rue gournod called coreleone( as in the godfather) You are right about some prices went to have a drink in one of the bars on the sea front and they wanted 28euros for a glass of wine !!!
would recommend Nice to anyone it is super and will deffo be going back

Whoops! Didn't notice the date of your post, but delighted you had such a great time. And what a coincidence re the Baracuda!!
You've put me in the notion for a return visit!