I can think of a few options, obviously leaving on 30th December.

Option 1 (fastest but not the best) :

- EN Praha hl.n. - Freiburg im Breisgau Hbf 18:28 - 06:17 178€ (89€ per person) for a private double sleeper

- TGV Freiburg im Breisgau Hbf - Paris-Est 07:08 - 10:17 20€ seat reservation (1st/2nd class)

If the night train is too delayed and you might miss the connection change in Offenburg instead : 05:45 (+ delay) arrival, 07:50 departure. Time for a coffee for example.

Option 2 (best for a good night sleep) :

- EN Praha hl.n. - Basel SBB 18:28 - 07:20 178€ as above (same train)

- TGV Basel SBB - Paris Gare de Lyon 08:34 - 11:38 or 10:34 - 13:38 29€ seat reservation (39€ 1st class)

Option 3 (as good and a bit cheaper, my favourite) :

- EN Praha hl.n. - Zürich HB 18:20 - 08:20 116€ private double sleeper

- TGV Zürich HB - Paris Gare de Lyon 09:34 - 13:38 29€ reservation (39€ 1st class)

In any case I'd book soon whichever option you choose. Trains will be very busy around that period.

Questions welcome !