I don’t want to cause any issues with immigration upon arrival. I am planning on a round trip ticket for Christmas break, but the dates are at this point unknown to me.
no problems not having a return ticket as long as you have your visa paperwork sorted- and you are right that it is easier to get switch over to coming/going during the school year.
Get to the airport early. Occasionally it can trigger extra security.
My kid did it, another country. Agree to have your paperwork and explanations in order. She didn’t know her return date, just more or less the window.