Sorry to say - that is a bit lame
I'm not sure if the fireworks are shown on TV here, but last year I managed to head out to the lake with a 3 and a 4 yr old and they enjoyed it a lot (after the initial scare from the loud bangs).
We got off at Stadelhofen picked up some hot tea from McDonalds right outside the station and headed over to the lake. There are a few fireworks that go off at midnight, with the main show starting around 15 mins later.
What we did last year was to put the kids to sleep a bit earlier in their daytime clothes and wake them up shortly before 11pm, and that worked perfectly.
Have I persuaded you to come along yet?
PS. Transport from Stadelhofen on the way back is absolute mayhem and I would not recommend it if you have a pram. I'm going to walk up to Paradeplatz this time and try to catch a tram back if I can.