What transportation options are available from central Zurich to Zurich airport and at what cost? We will be 4 people (2 adults, 2 kids). How long could it take to get to the airport on a Saturday? Also, how soon do we need to be at the airport for a flight to Paris (i assume that isnt considered an international flight needing immigration process).

There are local trains from Zurich main railway to the airport every 10min or so. The cost is about 6 or 6 CHF for an adult and it's about a 12-15min train ride.

How soon do you need to be at the airport? By whatever time your airline says checkin closes.

I ask about time at airport because here in the US there are long security lines and recommended time is at least 2 hours for domestic flights and 3 or more hours for international although checking close 30 mins before domestic flight, and 45 mins for international. They want to allow extra time so you can take off your clothes, throw off that water bottle and shampoo in the garbage can and go thru CT scan before you can clear the security

Switzerland has security lines too. And you need to wait on check in-lines. Your airline will tell you when to arrive - but I wold be at the airport 2 hours before flight time to be safe - esp when traveling with kids.

usually, for overseas flights, arrival at the check in should be around 2 hours prior to the flight...

The flight is to Paris - not overseas.

Why would you think a flight from Zurich to Paris is not an international flight? You're going through the security process, which tends to be very time-consuming and it can be a long way to the gate. We had to be there 2 hrs. prior to departure for a flight to Stockholm.

In contrast to others I would arrive at ZHR approx. 1 hour max. before departure.
I travel to ZRH regularly from another major European city and have never had a problem with that time frame.
As France is a Schengen country and Switzerland is associated to the Schengen zone there won't even be another passport check before boarding.

E.g. Swiss' check in for European flights closes 25 min prior to departure. This gives you an indication that the whole process of getting through security and going to the gate isn't that time consuming.

Taking the train to the airport is easy. From the main station it's about a 10 - 15 min. train ride to the airport. YOu can take various trains and there are departures about every 10 - 15 minutes.
If you are closer to the lake, the Stadelhofen station may be a good alternative. The S16 takes you non-stop to the airport from there in about 15 minutes. Departures every 30 min.
The cost for the train ride from either station is CHF 6.40.
http://www.sbb.ch/en/index.htm

wooops... misread...
for european flights, its usually 1 hour prior to flight...