Some readers would say that the children are doing nothing at the beginning of the story. Those readers do not have children of their own or they have never tried to keep kids inside on a rainy day. What the kids are actually doing is going stir crazy and driving the adults crazy.
. . . the children strained to get out. Their faces were red and bloated with the effort . . .
The kids have been cooped up indoors for a long time, because the weather outside is too warm to play.
It was still too hot to play outdoors.
The text tells the reader that the mom is doing her best to keep the kids occupied while inside the house. They had tea, took baths, and did basic grooming of themselves.
They had had their tea, they had been washed and had their hair brushed. . .
But there is only so much a strained parent can do. The mother can't handle the whining children anymore. She lets the kids out to play in the heat as much to relieve their tension as to lower her own stress level too.
"No—we won’t, we won’t,'' they wailed so horrendously that she actually let down the bolt of the front door so that they burst out like seeds from a crackling, overripe pod into the veranda, with such wild, maniacal yells that she retreated to her bath and the shower of talcum powder and the fresh sari that were to help her face the summer evening.
The story doesn't explicitly say what the relationship is between all of these children, but with so many in one house with a single named mother, I'm guessing that the children are all related somehow. I do not think that all of them are brother and sister though. My guess is there are some siblings, and the rest of the kids are cousins. It's like that in my own home. I have three young kids. My brother-in-law and sister-in-law have three young kids, and they live a mile away. Our kids are always together in one of the two houses. And yes, 6 kids under the age of 8 will drive you crazy enough to let them in the backyard to do whatever regardless of the weather.