I'm interested in why no one mentioned this.
You are going to a non-Orthodox household for a dinner. Much material exists to explain that sentence.
Remember we are supposed to hide our fasting, and not tell the public, for the reward from God is greater than the reward from man. It would be more imposing to try to assert or make a spectacle at a mixed gathering. If it were a total Orthodox gathering with the minority being non-Orthodox, then you could go full out. But since you are visiting a non-Orthodox household for the dinner we were taught that it is better to accept their food and not mention your fasting at all. What is worse, breaking the fast by pride of telling everyone you are fasting or keeping the fast in your heart that day while you keep the fact that you are fasting quiet? I hope I am making sense. And remember fasting doesn't mean anything if it is done just to meet the "legal requirements (think how the pharisees held the law). The best thing to do would just go to the dinner and have everyone eat what is given by the host.
Fasting by inquirers can sometimes dishearten them greatly. Fasting is a challenge. To get the balance of pray and fasting just right takes time. Many rookies keep legal and get sick, they over-fast, they don't know recipes to keep a balanced diet during fast times (mostly great-fast). Ease into things. Talk to your priest.
Don't be afraid to call him about this either! Orthodox priests are close to their congregations and inquirers and welcome calls like this fasting question. I wouldn't email him this question as you can't get the same amount of instruction via email as you could over the phone or if you can set up a 30 minute meeting at his office.