Wireless definately. No cables = no mess. Wireless Modem Router about £70 plus 3 USB wireless adapters at £25 each(Prices are approx) Job Done.
You may find that the ethernet cable route works out slightly cheaper. The modem router (I assume you want to connect to broadband on all three computers independantly) will be about the same so it`s the cost of the cabling and inconvenience against the cost of the wireless adapters.