I think there is a bit of over reaction going on here.

I for one would delighted if the museum cafe sold more interesting drinks. Their coffee is pants!

The museum shop already sells adult items like art pieces. It would be rather surprising if they also started selling Fosters to go along side this. Now I don't know what they propose to sell but let's not get carried away here until we do.

Having a licence to cover more than the number of people than you propose catering for seems like good planning to me. This means that you don't have to individually count the number of people in the park at any one time - this would be a massive expense, probably prohibitive for most events. But again, I don't know the exact plans and though I would be surprised at a heavy metal concert (LOL) it would be good to find out more before criticising the idea out of hand.