We had our DS2's first birthday in a small local park. It was just a short morning tea, nothing fancy. No decorations or anything, just food. We did bring some folding tables and folding chairs (mainly for the older people). We didn't get council approval (I don't think we needed it!). There were probably about 30 people all up.

One thing, this park I'd chosen (as it had a good playground, was in a sunny, but sheltered spot, near to our house) didn't have toilets. I made sure to mention that on the invite so that people could go at home before they came. I did bring a potty in case any kids needed it. It was fine, but it was a short party (only 1hr).

Hope this helps!