Hiya
In February my boys and I took a day trip to Paris and it was great! They're older than your kids but I'm sure you could still get a lot done.
We left the Explorers Hotel at 10ish and did the following:
Got the train direct from DLRP to the Champs Elysee where we saw the Arc de Triomphe and climbed to the top

- then we took a stroll along the Champs Elysee itself; we stopped for lunch and next went to The Eiffel Tower - went to the top there too but couldn't see anything as it was too overcast. Next we went to Notre Dame and spend quite a while inside; then we walked to the nearby Hotel de Ville just to see it and then, The Louvre, to see the highlights (will do a more indepth tour of it at another time). Afterwards we strolled through the Tuileries Gardens in front of The Louvre and finally, got the train back to DLRP. So we got quite a lot done. I'm sure you'll get to see a lot. Make a plan, especially for the Metro (or buses, whichever you're using) to save going back and forth.
The Paris Visite is expensive and would not be cost effective for an adult for just one day - 18 euro. The Mobilis 1 day pass is only 12.50. However, you can get a (one day) Paris Visite
child's fare for just 9 euro whereas as far as I know there is no Mobilis child's fare so I
think the wisest thing would be to buy one adult Mobilis 1 day (zones 1 to 5) ticket and two children's 1 day (zones 1 to 5) Paris Visite tickets for the kids!