Hi, you might consider staying in Zurich overnight. Everyone will be tired and jet lagged when you land and further travel may be really hard particularly as you are travelling with elders and children.
Zurich is a lovely, small city that is nothing like most people think. The Old Town is gorgeous and the main areas for visitors are in a compact area that is very easy to access. The public transportation system is efficient, runs frequently and is clean and safe. The kids might enjoy a few hours at the zoo which is just a 10 minute tram ride from the main station and, of course, there are lots of benches for the elders while the kids can run off a lot of stored energy!
Priceline often has some great deals if you bid on hotels for central Zurich. It's pretty easy to get a room in a 4 star hotel for around US$150 per night. It's usually the Marriott or the Crowne Plaza. The Marriott is a bit better located as it is less than a ten minute walk from the main train station but the Crowne Plaza is also very nice and has a major tram stop just about a 4 or 5 minute walk from the hotel. It's about 10 or 12 minutes to the main station from the tram stop.
You might also want to consider using a transfer limo company from the airport to your hotel. I like one called Check-In Allways as they are reliable and their rates seem to be very fair.
You may also want to consider sending your larger luggage ahead to Lucerne. It's a service offered by Swiss Rail, it's totally reliable and safe (many of us here don't know what we would do without it and use it on every trip). If you arrive early in the morning and can send your larger luggage by 9AM from the Swiss Rail luggage office at the airport, the cost is 22 francs per bag for it to arrive that evening after 6PM and 11 francs per bag for it to arrive the next evening after 6PM. If you do this, you will really ease your travel load for getting on and off trains, etc. Just pack so that you can live out of a smaller bag for the overnight if you stay in Zurich or until the evening if you go on to Lucerne.
There is an excellent tourist information office at the main train station in Zurich where you can get a pocket sized map as well as advice on transportation, etc.
Hope this helps.