The building of the venue
Right next to the venue (and the hotel) is there a giant shopping mall, Lala port, where you can find almost every kind of shops. There is also a big electronics store, Nojima.
Food (google map)
On the 3rd floor of Lala port, there is a big food court, and also restaurants around it. Around the Kashiwa-no-ha campus station, there are also some restaurants and bars. The convenience store in front of the hotel is open for 24 hours.
At least around the venue and the hotel, you can always find free wifi.
At least around the venue and the hotel, you can pay by credit card for almost everything. You are recommended to check out if your credit card is usable in Japan, rather than preparing much Japanese Yen. Also, you can easily find ATMs on the ground floor of the shopping mall.