Should I have said no?

Let me start off by saying that my MIL is in a rock band. It's a Motley Crue tribute band.

This past weekend she was having a benefit for the Hurricane Harvey Victims, so all ages were welcome. But after 8pm no one under 21 was allowed. Because the benefit was going to be at a bar. My husband and MIL really wanted my son (which is 3) and I to go. My MIL asked the manager if he'd allow her grandson to go in to see her perform. (Where she was singing it was outside, so you did have to go in through a bar.) The manager said that was fine. She was going to be on stage for an hour. So my husband and I showed up late. We got there at 8:50. So we went in and we were only able to see her for 5 minutes. We did have our son with us. As soon as we walked in I saw this lady starring at us ugly nodding her head. The whole 10 minutes we were outside this lady was giving us ugly looks. Of course we would never willingly take our 3 year old to a bar! So right after her show and she acknowledged that we were there we walked out. My son was so excited to see his grama singing away!

So my question is this, should I have not brought him to the bar at all ? After that lady giving me really ugly looks made me feel like a bad parent.