I'm looking for a word for the things at a place where children play on Swings, Slides, Seesaws, Climbing Frames, etc. Is there a common word in English for these in general? Like in Indian languages, we say, "jhoolay झूले (plural)". After googling for a while, I could only get the phrase "outdoor toys". I don't think it's that suitable word which I'm looking for or it may be. The word referring to those things in general should be able to be used in such sentences: Our children are playing on/at/with the _____ (plural noun). There are ____ (plural noun) in that park.
I would refer to that as "playground equipment".
In regards to your example sentences:
For the first, I would just specify what specific piece of equipment ("Our children are playing on the slide") or just speak in a generalization ("Our children are playing at the playground").
For the second, I would say "There is a lot of playground equipment at that park".
In American English, there is a swing set, which is the frame with several swings and can include an attached seesaw and/or slide. Families might have one in their back yard. And a park might have a larger version.
But a park might also have several stand alone seesaws, slides, etc., which I would just call playground equipment.
But both adults and kids will talk about playgrounds (the 'ground' at a park on which kids play), and it is assumed that a playground includes such equipment.
Do you wanna go play on the playground?
No, that playground is stupid. All the swings are broken.
Okay, then let's go to the other park—it has a great playground!
(Meaning: the 'play equipment' and 'play structures' at this second park are outstanding and fun.)
Other words besides playground equipment include park and play structures and park and play systems. These are mostly technical words. Your average American will just say playground. They might mention specific things, such as the swings, slides, seesaws, humongous outdoor play house, which certain parks and/or playgrounds may have.
I take it that you want a hypernym of "the things at a place where children play on Swings, Slides, Seesaws, Climbing Frames, etc." As mentioned in other answers, you can use playground equipment. I'd like to add another alternative: recreational equipment.
Wikipedia uses this term on the page Playground:
Modern playgrounds often have recreational equipment such as the seesaw, merry-go-round, swingset, slide, jungle gym, chin-up bars, sandbox, spring rider, trapeze rings, playhouses, and mazes, many of which help children develop physical coordination, strength, and flexibility, as well as providing recreation and enjoyment. Common in modern playgrounds are play structures that link many different pieces of equipment.
Note that equipment, like furniture, is normally used as an uncountable noun.
English has no exact translation or hypernym for جھولے , so I suggest we use "rides" Like the Entry in Oxford Dictionary (https://en.oxforddictionaries.com/definition/ride) (2A roller coaster, roundabout, or other amusement ridden at a fair or amusement park.) (Example from the same source: ‘When I was a kid I loved the rides at amusements parks - the Zipper, the Swings, the Polar Express and even those cheesy haunted houses.’)
You can say playground apparatus, recreational devices, but I think the word 'Rides' is more appropriate.
This amusement park/playground has all kinds of rides.
rides: a large machine at a funfair or amusement park that you ride on for fun or excitement; an occasion when you go on one of these.