I didn't convert from Protestantism but my mother's family is heavily Protestant. I think you should invite them. The beauty of the Orthodox service and everyone else at the church being happy for you might have a little impact on how they feel about the Orthodox faith and about your conversion. My Southern Baptist grandmother wasn't very happy about my conversion either but that has slowly changed and she now accepts my conversion. I would invite them. You'll never know if you dont ask! Anyways, Congratulations on your Baptism/Chrismation...May God grant you many years!