They should come if they are willing. Focus on the joy of the day and the confidence that drew you to this decision, and seriously struggle against any thought about them, their possible concerns, potential questions, etc. Don't worry about needing to have all of the answers. New converts often believe that they need to demonstrate to their family that they know everything about the faith that they are joining; while their families likely know very little about their own faith. If they have the concern that you are jumping in to something you don't understand, you can simply say that you have studied and prayed a great deal about this and you are confident that joining the Orthodox Church is the will of God, and you can humbly explain what led you to this decision. Regarding specific questions, however, answer if you feel able to do so humbly and clearly; but if you are not able just be willing to say to them that you would be happy to look into their questions and get back to them with an explanation. Resist the temptation to engage in debates, and turn down provocations towards this end. If there is humble inquiry, certainly respond as you can, but a person who just wants to prove you wrong is futile to engage. Most of all, pray for them and deal lovingly with them, realizing that they too may in time join the Church if you are able to be a good example of humble, Christ-like love.
When my wife and I were married in the Orthodox Church, her Protestant parents came even though they are quite hostile to our Faith. Since years ago we were married in the church that they still attend, it is understandable that they would be offended somewhat by our being married in the Orthodox Church, which signified perhaps an even greater rejection of their faith than when we were baptized in the Orthodox Church years ago (they didn’t attend the baptism, though we were living very far from them at the time). After the service, my father-in-law said, “that was awesome”, whereas my mother-in-law looked like a walking corpse. You can’t help how people respond to things, but it is good to invite and pray for such people, maintaining hope that perhaps their hearts will soften and God will enlighten them in time. Remember, it is God who can enlighten people from within, and it is not really up to us to convince people of anything, though we should do our best to explain our faith, and to live it first of all.