Hi,
Morges has very good playgrounds (especially the one by Morges temple and the one in Vertou). A little train runs around town every sunny day in Summer for more info regarding the train
http://www.morges.ch/view.asp?DomId=298
You might want to go to
http://www.edukids.ch it is in St Sulpice between Morges and Lausanne to meet other mums.
For sunny or rainy days, Signal de Bougy
http://www.signaldebougy.ch/ is a great place for the all family (they have an indoor play room in the restaurant building) here is some info about the place in English:
http://www.myswitzerland.com/es.cfm/...ports&id=17171
For sunny or rainy days, Planete Jeux is a good place as well,
http://www.planete-jeux.ch/ but it is a bit of a drive from Morges and a little expensive…I would recommend it for slightly older children than your son.
A visit at the zoo might be fun as well
http://www.zoo-servion.ch/
Good luck and have a lot of fun!
Vanilla