I would recommend this app for ages 15+. It's pretty entertaining, but most of the users are WAY too young to legally be on the internet (In the US, you have to be at least 13 to have an account on major social media such as Instagram or Snapchat. It is higher in Britain.
I saw groups such as "Make friends ages 7-12" and "make friends 9-14". 7-12 year olds should not be permitted to be largely unmoderated on the internet- This is worrying considering that they're likely still in elementary school- as young as 1st grade.
Some users I have seen say they are as young as EIGHT.
Online games that are oriented at children, such as Roblox or Animal Jam have to follow certain restrictions such as not allowing children to post/give away their personal information, email, and also must follow restrictions on what they do with the children's data. Companies cannot save any of their information.
They have to provide a safe environment for children under 13 which Picnic doesn't do at all- it doesn't even pretend to.
The businesses could be fined for not complying with this, and it gives them a bad name. It becomes a safety risk.)
Picnic does NOT appear to moderate chat for different age groups and it also DOES NOT ask for a birthdate to sign up which may be why this is allowed.
I would not recommend letting your child use this app. It has next to NO safeguards for children and teenagers, and moderation seems weak at best and nonexistent at most. (Some communities, in place of "rules" have a shrug emoji.)