I did a similar thing at home. I bought a small Behringer 8 channel mixer and a pair of Mackie TH-15a Thump powered speakers. Cost about $800 Canadian dollars. Don't forget you also need cables. The mackies can take a single line in directly. I get pretty good sound, although to really get the bass going I'd pick up a subwoofer somewhere down the line. I bought one speaker and the mixer for my e-drums, and added the second one later.
If you don't need to have speakers, I use a jamhub for band practices at my house now. Every one runs their instruments and mics directly into the jam hub, and you play listening to headphones. You have individual volume control over all the other instruments/musicians.
It's transformed jamming at home for my band. You could have one e-kit panned left, and one right in your headphones for playing together. They have a couple different models, depending on the number of inputs you need. http://www.jamhub.com/
Or finally you could pick up a keyboard amp, many of them have a couple input channels, but the sound quality can vary a lot, so I'd try them with drums plugged in to see if you like the sound.
The link above to the vdrums site the othe poster mentioned is excellent information.