A "spiral" slide. (Which is really a helical slide . . .)
The Playground Kidders are the playground kidders
Either can be correct, depending on its use in a sentence: "Mel and I are at the playground" or "She found Mel and me at the playground."
Trash and old playground items to be replaced by new playground items.
The noun playground is a countable noun. Singular: playground Plural: playgrounds
No, it is not a preposition. The word playground is a noun.
A playground has no fixed size
playground equipment
It depends what playground it is; they can be various sizes.
Playground for Life was created in 2008.
Yes. An adventure playground.
Marcy Playground was created in 1997.