filter from osm-xml


I am newbie to OSM and its data structure and software(s) but gps user and quite familiar with digital maps in general.

I am interested in a specific map that might be generated out of osm data.
I am looking for registered playgrounds (#7207) in the map soley displayed in a layer of a map.
To prevent vanishing this layer in the background of a GPS-Software, it would be helpful, if waypoints are generated out of the corners of
each area (a single midpoint would be preferred but this needs to be calculated).
I have access to online osm xml data and can process it in CompeGPS Land (although I think there are bugsā€¦). With this software I was able to create such a map (single layer type 7207). But when using this with a other maps, vector shapes are not filled with defined colour. So it is not visible (apart from shape line but they are so tiny).

Are there recommended osm tools that can do the job ?
What would be the list of sub tasks (that I can learn how to do it) ?

As osm xml is text based data, a script may do the job ?