I think that the ct Yd is the cheapest hotel if you need 2 rooms for kids but most hotels will let you put an extra bed in the room if they are under 15 years old. The Rome Marriott Park Hotel is the largest Convention Center hotel in Europe. and has a Spa & wellness center and a large outdoor pool . The Courtyard Rome Central Park in Rome is nice to have a hotel at the park with kids but it is in the business district close to Villa Madama, St. Peter's Basilica, and Stadio Olimpico. I Stayed at the Venice Courtyard next to the airport and took a 20 minute bus ride to Venice. The bus stop is right across the street from the hotel and the hotel will sell you tickets.