Hey Bombshell, they have evening (after-work) and weekend classes too, so you can even drag DH along! I have sent my DH when I couldn't go, and even he loved it (and there were other dads there, so he didn't feel stupid).
Anyway, Emma Rose was about 8 months when she started, but they start babies at 3 months. When my friend was visiting from Palmy a couple of weeks ago, we took her and her 14-week old along, and he loved it. The classes last about 45 minutes but they move fast through different activities so the short attention spans are catered for...
Their website is www.mygym.co.nz if you want to have a look. It is fast becoming the highlight of my week... Is that sad or what? LOL