Help battery acid???!!!?

Okay so I wanted to go on the wii fit last night but there was White powder over all the batteries, the reason I checked the batteries bit was because I thought it had none in it. I took it in the kitchen and was going to take the batteries out but got side tracked by something else. My mum took them out bu their is now White powder all over my kitchen work surface and in the battery compartment in the wii fit board. How should I clean this up safely? (I'm 13 btw and my mums at work)