That service uses a SQL syntax and all you would need t do is either make multiple calls or adjust the start / count parameters - the (0, 1000) - to whatever you need. I would recommend making multiple calls and just paging through the results as this can be programmed dynamically.
I queried "select name, woeid from geo.places.children(0,1000) where parent_woeid in (select woeid from geo.places.children where parent_woeid in (select woeid from geo.places where text="india" limit 1))" to populate all the disctricts and their woeid under India. And using the woeid I tried to populate the rss "http://weather.yahooapis.com/forecastrss?w=12586374&u=c". But the weather is not getting populated. I checked with the yahoo woeids. The given woeids are not correct while querying. Plz help me to solve this issue.