Paris in 1.5 days - and then some

That is a lot to pack into three days. The museum pass must be used for consecutive days, so you can't split it between your two stays. I suggest you get a museum pass for your first stay, so you can use it for Versailles, then pick two museums for your first day. Keep in mind that the pass does not allow you to skip the security line. Fill the remaining time on day one with a nice lunch and dinner, some walking, and perhaps a sunset river cruise. For your second stay, pick maybe one museum, and fill the rest of the time with exploring a neighborhood like le Marais or Montmartre or the Latin Quarter. If you want to get up high for the view, try the Montparnasse Tower where there is a relatively short line and the cost is about 13€, or Sacre Coeur, where the view is free. Another free view is from the roof top of Galleries Lafayette, and where the glass dome inside is eye boggling. Paris is more about soaking up the ambience than checking sights off a list. In other words, less is more. Bon voyage.

No time for the catacombs or Pere Lachaisse, but you could work around this.

PM TUE 28 MAR
Sacre Couer Basilica
Eiffel Tower

WED 29 MAR
Pantheon
Jardin des Tuileries
Louvre

THU 30 MAR
Versailles

PM SAT 8 APR
Seine River Cruise

SUN 09 APR
Musee Picasso
Pompidou
Musee d'Orsay

AM MON 10 APR
Sainte Chapelle
Notre Dame

Be aware that Versailles takes most of a day. Even if you can squeeze yourselves through the crowds to get through the palace and a glimpse of the gardens and hop on the train back to Paris in a few hours, you'll be fairly exhausted from doing so.

Something to think about...Everyone I've talked to without fail and all the guide books I've read have said the same thing- that Versailles is a whole day. Have a great trip whatever you decide! Paris is always a good idea as Audrey Hepburn stated.

In this case, less is more. Pick 2-3 must sees or must dos. What really interests you?
The advice to assume you will be back someday is good and helps to narrow the focus.

Yeah - no way you can come close to getting that done. If you arrive at CDG at 1:00 - you'll likely not get to Paris until 2:30'ish - 3:00 (depending on going through customs). Then you have to check into your hotel. So best case scenario - you can start your sightseeing around 3:30. So you have a few hours on the 28th and a full day on the 29th. Pick a FEW of the things you really want to do and concentrate on those. I don't know what's important to you - but Notre Dame is near Ste Chapelle - so those two could be done at the same time. If you have the museum pass - you could jump into the Louvre to see a few of the highlights (Winged Victory, Venus de Milo, Mona Lisa) then get out of there. I'd personally choose the D'Orsay over the Pompidou - but that's just me. And I'll echo what everybody else has said - Versailles is a full day. If you're going to commit going there - don't cheat yourself.

So pick a few things you really want to do and do and enjoy those. It'll make for a far better trip than just rushing from site to site to be able to say you saw it.

Def narrow this down to what you most want to see, perhaps picking 2-3 different things: 1 museum, 1 church (St. Chapelle also has evening concerts), and 1 garden/stroll/dinner. Don't rush trying to fit so much stuff in that you don't enjoy just being in Paris.