Rail Pass or Point to Point Tickets

I assume you're flying from Rome to Paris, which is the best plan. A Select Saverpass for 5 days of 1st class travel in these 4 countries will cost about $454 per person tomorrow. Two kids under 12 would travel free with you or youths aged 12-25 will pay a bit less than the prices above, still in 1st class. The Italian routes require seat reservation fees adding up to $45 per person with a rail pass (but built in when you buy longer-distance Italian train tickets). The pass gives you 1st-class seating options and some additional coverage and discounts on boats and lifts around Luzern. Details at http://www.ricksteves.com/travel-tips/transportation/trains/select-pass will be updated in the next day or three. You probably won't cross any significant portion of Austria, but if you travel Munich-Luzern via the Austrian border at St. Margrethen, then you must pay about $5 more before boarding the train.

You can buy full-fare, 2nd class tickets for all the trains mentioned for about $475 per person with no particular need to reserve ahead. Or you could cut that total quite a bit if you lock in advance-discount tickets up to 3 months ahead for specific dates and times for your longer rides. Paris to Bayeux is the cheapest trip at $50 each way, and least opportunity for advance savings. Airport trains are cheap and not part of the equation, just as you took other side trips out of the equation. See also http://www.ricksteves.com/travel-tips/transportation/trains/buying-tickets.

We have tried both ways travelling over 8 months in Europe in the last 2 years. First time train passes (2 adults) cost approx 2700€ for 2 x 3 month passes. Next time we booked point to point online some months before departing. Cost for 3 months approx 500€ for both ( not each!) huge savings. We booked online on the DB Bahn site for almost every country and I initially put in 1 adult, thinking we could calculate the cost from there. One example, price quoted for one person was 25€ but when I entered 2 people the cost was only 29€ for the 2 of us! Go point to point, but book well ahead we have experienced the savings ourselves.
The difference between 1st and 2nd class in most countries is nothing. You often travel in the same carriage, same seats etc. and the only difference is a glass partition separating the 2 classes. Don't waste your money on 1st class it no better than 2nd. Happy travels!

Committing to advance purchase nonrefundable tickets, you should be able to do this for about $1000. Almost half the price of rail passes. Travel 2nd class, which is perfectly fine.