Both Laure and I live in Geneva, and although we do enjoy some skiing away during winter, the rest of the year there are tons of things to do with our children right here. Spring and Summer are the best for obvious reasons, you can have lunch on countless terrasses, from country side charming to city spots, stroll around the lake or fields, and of course apero is a must.
In the city, I like to have breakfast in the morning on Place de Bourg de Four (the pains au chocolat at Arn are truly decadent) and let the kids run around with the promise of a spin on the carousel later.
For lunch, my personal favourite is the Collonge Café (in Collonge duh), the food is amazing, the terrasse is beautiful and borders a public park, meaning your children are entertained while you sip your glass of wine/spritz.
In the afternoon, we sometime go for a poney ride in Presinge, a stroll in the park Bertrand (l'Athénée is a great place for goûter), feed the ducks on Ile Rousseau or get ice creams by the Jet d'Eau. Some chocolate from Laderach never hurts either.
These are only a few places we enjoy, feel free to comment with more so we can explore next time!