How to celebrate our kid’s 1st birthday (new to London)

Hi,

So we’re new to London and our kid’s 1st birthday is coming up.

We don’t have our immediate family here, and we only know a couple of friends with kids.

How should we celebrate the birthday?

Most venues we have looked at require “minimum attendance” of 10 kids.

Is there a park we can go to have a small picnic with our friends who have kids?

Any other ideas?