Sounds fantastic Smurfgirl! It really depends on the resturant and what you expect your boyfriend might wear. Some resturants are posh but fairly casual, some not. Equally some men dress up more than others. If I were you, and it sounds like you might feel more comfortable underdressed rather than overdressed, I would wear a dress or skirt/top that is quite fashionable and you feel comfortable in, or even trousers and a nice top. It sounds like 'smart/casual is what you are aiming for. Trust your intuition and make sure you feel good in what you're wearing. That's the most important thing. Let us know what you decide. A trip round the shops trying things on might help!