Are seat reservations on Swiss Rail necessary?

You don't need to reserve seats at all. Trains are frequent and there are always seats available. While technically you can make seat reservations in Switzerland, in practice it's very rare for anyone to do this. In fact some locals aren't even aware that seat reservations are even possible:) Save you money.

Thanks Michael for your quick response.

The only trains requiring reservations are the tourist trains, Glacier Express, Bernina Express, etc. and a handful of EC International trains. Other than that, nobody gets seat reservations. Find a seat and sit.

1st Class compartments will even have more seats available than 2nd Class. Swiss Trains are wonderful and Swiss Pass is perfect for just hopping on and off wherever and whenever you want.

As noted, esp. with the first class pass you will have no trouble finding seats. Depending on the size of your family and the particular train car you may not all be in a group but you'll certainly be within striking distance.

Also note that apparently if you find more room in second class or just prefer the layout you can sit there too, the conductor may give you a funny look.

Make sure you fill out your passes EACH DAY with every individual trip. Most conductors will let it slide but you might find one (like me) who will give you a lecture about it. And then after your trip, send the passes back to the prepaid address listed (make copies for your records). His point to me was, the European/Swiss train companies use this info to figure out how to divvy up the pass money pie each year. After a few months you'll get your passes back along with a thank you gift (I got a little train shaped flash drive). Redact any personal info before sending.

Thanks everyone for your insightful responses. This takes a load off my mind as my itinerary is rather fluid. Much appreciated.