"Playground" usage

Question

"Playground" meaning according to dictionary.cambridge.org.

1. An area designed for children to play in outside, especially at a school or in a park.
2. A place where a particular group of people enjoy themselves

I'd like to have a sentence based on conditions:

1. There's a river.
2. Many children often down the river to play or to fish.

My question:

Could I use the word of "playground" in this case?

"For many children, the river is to be a fun playground".

Answer 1

I find that use rather odd, but I would say

Many children make the river a playground.

or

Many children make a playground of the river.

The use of "make" implies that the river isn't really a playground ("an area designed for children to play in") but that they regard it that way.

One other point: "is to be" means "somebody is planning that": I don't think it's what you mean here.

Answer 2

When the word playground is used figuratively to refer to any place where people go to have fun, it could be used of almost anything:

The town dump was their playground.

The Riviera was their playground.

The riverbank was the village playground.

Virtual reality was their favorite playground.