Would next to each other also be an option? Then I could recommend the Bugaboo Duo Donkey, you can also add one bassinet and one normal seat on it but the children sit next to each other and can either be facing you or the face forward. If they should be facing each I can recommend the Brevi Ovo Pram, a friend has this pram and likes it very much and it is also quite cheap for a double stroller. But you can also have a look on [url=http://www.prams.net'>www.prams.net[/url'> and look for tandem prams, they have a lot of strollers in this type.
Do you prefer cities or beach/mountains/nature?
I loved visiting Italy especially the Toscana area but I'm not sure if it is suitable for children. How old are your kids?
Also Amsterdam and Netherlands in general is nice, you can also do a lot of things there like riding with the bicycle around the country etc.
