Hi again, Michelle:-)
Since I have not tried substituting orange juice or orange extract in this recipe, I'm not absolutely sure what to tell you. I think that if you want to eliminate the alcohol (Grand Marnier)that orange juice would definitely not be the way to go. It would water down the consistency of what is essentially a custard and probably ruin the dessert. I think that I would try a little bit of orange extract and use some orange zest, or maybe just use some orange zest. If you decide to make the recipe with orange extract and orange zest, or just orange zest, let us know how it turned out. I think that the best thing to do would be to try this before Christmas Day and see how it turns out. That will help you make a decision as to what to include in your final recipe. Good luck and Merry Christmas, Michelle:-)!