Hi Liliana,
Great choice Girona, a wonderful place. A very nice ancient city. It's 40 minutes by car from Barcelona city, half an hour from the Pirinees and 30 minutes from the beautiful beaches of the Costa Brava.
To Stay in Girona with four kids my advice is a casa rural (rural house).
Casas rurales are ancient farms, country houses or even medieval manor houses completely refurbishided and nicely decorated. They have all modern comforts. They usually have gardens and terraces and some of them have swimming pools.
You can rent the whole house or only the rooms you need.
Here you have one useful link. You can search your house on the map included in the web page.
top rural