Malpensa is not only 6 to 10 km from the center of Milan – it’s almost 50 km. The bus between the airport and Milano Centrale train station takes about an hour. I’d be surprised if you find a hotel in Milan that allows more than 4 guests in a room. As you’ve found out, that would be fairly rare since most hotel rooms are fairly small.
Of the one’s you’ve listed, I do know someone who has stayed at the Jet Hotel and liked it – they have rooms for 4 or 4 people for 125 or 145 euro per night respectively. You might also try the Novotel – they’re offering a special on a triple for 119 euro per night: http://en.venere.com/hotels_cardano_al_c…
I live south of Verona. When I fly out of Malpensa, I stay near Milano
Centrale and take the bus to the airport for early flights. The hotels aren’t very convenient – there’s nothing in the area. This place near the station allows up to 4 guests in a room. A room for a night is 90 euro on the night you’re looking for (80 euro for three people in the room). Hotel Delle Nazione is also 80 euro for 3 in a room: http://en.venere.com/hotels_milan/centra… I’ve stayed at this one and liked it: http://en.venere.com/hotels_milan/centra… (105 euro for a triple).
Another option is to stay near the Cadorna station in Milan and take the train directly to the airport – about a 45 minute ride. The hotels in that area are likely to be more expensive though.

We did. Check out this hotel simple but cute http://www.booking.com/hotel/it/lapistah… Scoobit.com is a safe website I’ve used many times so far, and you can book on line. Have a great time