I feel so bad I wanna cry for reals!

During this time we have decided to buy bikes for our family. Our youngest is 5 months old, can sit up by holding my fingers, stay sitting up assisted, can hold up his head no problems with all he can do I decided I was gonna buy a bike trailer so that he and our daughter could ride in since they can't ride bikes.

Today we went on a long bike ride it was really fun and sunny out, it was awesome, he sat there the whole time looking around I was excited. After we got home my mom messaged me (pics below) saying how his neck looked strained, and that he was too young.

She sent me different things about it and each time made me feel even more horrible I did that. I have 3 kids but never had a bike or trailer so I didn't really know I just assumed he was fine. It pretty much ended with her saying we should put him in his carseat in the trailer that it would be better for him. The one thing I love about my mom is she isn't invasive, she's straight forward, she knows I know what I am doing but if its new like this she will give me her opinions.

Only reason I was short responses with her is because I felt bad and like a horrible parent for putting him through that. I'm the type to learn from her mistakes so it won't happen again....