Online vs Airport ..1st class or 2nd

I found the following online. Since the Swiss Family Pass is tied to at least one parent having a Swiss Rail Pass. The best place to buy looks to be the Zurich Train Station. Just buy a ticket from the airport to the central station and buy it there.

Swiss Family Card
Children under age 16 travel nationwide on public transport free of charge when accompanied by at least one parent holding a Swiss Travel System pass or ticket. The complimentary Swiss Family Card is available on request from all Swiss Travel System points-of-sale worldwide and within Switzerland.

And even if not accompanied by a parent, children still receive a 50% reduction off the entire Swiss Travel System range of tickets.

Advantages at a glance
Children under 16 years of age accompanied by at least one parent (holding a Swiss Travel System ticket) travel free of charge with the complimentary Swiss Family Card
Children under 6 years of age who are accompanied by a holder of a valid STS ticket travel free of charge
Information
The Swiss Family Card is obtainable at nearly every Swiss railway station as well as all points-of-sale worldwide
Children under 16 years of age not accompanied by a parent, receive 50% discount on the Swiss Travel System tickets & passes

You can buy your Swiss Pass and get the included free Family Card at the rail station in the Zurich Airport. There is a ticket window with an agent you can speak with.

A First Class Pass does not mean guaranteed seats. For any Swiss train that allows reservations (generally the InterCity trains, not regional trains) you make those separately and pay the fee.

First class generally has fewer people, but we have very rarely had trouble finding open seats without reservations. And many of the trains serving areas like Lauterbrunnen Valley do not even have first class sections. Nor do the cablecars or gondolas.

Since you are traveling in late September, crowded trains should not be an issue at all.

First class on a Swiss Travel Pass does cost 50% more and I'd consider it not necessary, unless you're wanting to reserve particular panorama excursion trains like the Golden Pass, Chocolate Train, Gotthard Express, or Glacier Express that market some particular perks in first class. Consecutive-day passes can be issued as e-tickets, while flexi passes purchased online do have to be delivered to you.

I personally don't think that first class on Swiss trains is worth it...it's quite a bit more expensive and the first class seats and cars aren't that much more superior to second class. Seats are a bit wider with a little nicer fabric and it's not quite so "plastic" as the second class car but honestly, I wouldn't pay the difference for that.

We bought the pass at the airport but we have two adults and two youth so I do not know about family card. If we had bought it ahead of time we could have been on an earlier train but it really didn't matter as the route from Zurich to luzern on our arrival day was under construction and we had to bus part of the route.
I will say we did buy first class passes. We will be riding 3 of the named train routes but that didn't make up our mind. We are tall. I am the shortest at 5'9" and it is the leg room that is an issue for us. yes you do have to ride second class on the small regional trains and we did yesterday and there is no leg room at all. I am glad we will have more leg space on long train days.

Thanks for all the advices..
That Intel about the Zrh-Luzern construction pretty much seals my decision to stick with the 2nd class.
Has anyone tried getting the pass thru the app?