Question for breastfeeding teachers!

I am a new breastfeeding/pumping mom and just came back to work last week. On a normal day, my schedule is perfect for pumping during my planning and lunch times, so I dont have to have my class covered. We’ve had a schedule change on three separate days since I’ve been back, so I’ve had to have someone cover my class while I take my bag and go pump. My kids (4th grade) started to ask where I was at on the third day. I told them I had a meeting. However, starting tomorrow, and all through next week, we will have an alternate schedule that will cause me to have to have my class covered to pump each day. My question is what do you tell your class youre doing during that time? I feel like I can’t say “I had a meeting” for the next 6 days and then also those other random schedule change days throughout the year without them getting suspicious lol. And obviously I don’t owe them any explanation, but you all know how nosy kids are and how they start to make everything their business and start looking at you extra close lol. The other day when I was coming back from pumping while a teacher covered my class, one of my students saw me getting out of my car (I had to pump in my car because no where to go on campus 🙃) and that was the day they started asking where I was. I’m just not sure how to navigate this as it’s already awkward and inconvenient, so thanks in advance!