Then I would look at one of the fast primes. I am not very familiar with the Sony lenses, but I am sure they have a 50mm prime that is probably 1.8 or 1.4. This was a "normal" lens in the 35mm world. In dSLR's the 30mm is probably the equivalent. If you want something with a little more power most makers have something in the 85mm catagory.
I am guessing when you talk about taking night pictures easily your talkin of things like spectro or something. If your talking about pictures of the castle or fireworks, your money would be better spent on a decent tripod.
If your talking about pictures of your kids, your money might be better spent on an external flash.