My boyfriends mom wants me to take him banana bread on my plane trip to see him. What is a nice way to say I dont have room?

She wants to plan my trip for me and I am 25 and he is 27 going to be 28. I dont want to pack loafs on the plane lol. Am I being really rude? I am limited for space.
Update: Thank you for all the funny comments, it truly made me laugh out loud.
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