Help with itinerary--Croatia this December with family of 5

At this time of year and with such a short amount of time, why not stay in Zagreb and do day trips. These could be added to your list:

Ljubljana - 1.5 hours. Perfect for one day, nice small old town.
Postojna - 2 hours. Caves and predjama castle (in Slovenia)
Krapina - 46 minutes. Great museum about the discovery of a Neanderthal site where remains were found.
Trakošćan - 1 hour. One of the few real castles in Croatia. Also has a nice lake to walk around.
Samobor - 27 minutes. Birthplace of Kremšnita cake. Also great šampita, my preference. We drove from Rijeka just to have some.
Karlovac - 39 minutes. Town where 4 rivers meet and they have a nice, but small, aquarium.

These are just a sample of small towns nearby where you can spend a nice day. We’ve been to all these places and are never disappointed by the friendly people, great food, and interesting history.
Also, Zagreb has a few days worth of sights.

PS. We always stay at the Hilton Canopy cause they have parking. It’s not too expensive.

Thanks for the insight. Very helpful.

Another reason to consider one base in winter is the weather. You would have time to consider each days forecast and rearrange plans accordingly. That is harder to do if you are moving around and so have only that day or two in a given place. Also include in your plans Christmas markets. Unlike some other ones in Europe the Zagreb version runs through the first week of January.

If we wanted to have one coast day, would it be worth planning an overnight trip to Istria? Or is there enough day trips out of Zagreb to keep us busy?

Croatian tourism completely changes in winter. In the summer it is based on the coast but in winter time the top three places are Zagreb, Opatija/Rijeka, and Istra by a significant amount - Dubrovnik was fourth last year but had 1/3rd of the tourists for Istra/Primorje. So Zagreb, Opatija, Rovinj, and any city less based on tourism (say Varaždin) will have open restaurants.

Zagreb has an excellent Christmas market, there will be lots going on, and weather has not been so bad recently, just mostly cold.

Plitvice Lakes will be partially closed but could be very beautiful especially if it has snowed. If you wanted to stop at the coast I would look either at Rovinj or Opatija.

There is an alternative trip where you do not take day trips. I would go to Graz, it's about 2 hour drive north of Zagreb, all motorway, you could stop at Trakošćan and maybe Krapina en route, weather permitting, then stop in Ljubljana/Bled on the way back.

Note however all of these motorways can close for snow, especially the A1/A6 from Zagreb to the coast. You will probably be fine, may have to be flexible.

Based on the feedback, does this seem doable? We fully understand that weather could require us to move things around or cut out portions of the plan.

Saturday: Arrive in Zagreb
Sunday: Explore Zagreb and enjoy a food tour
Monday–Wednesday: Day trips from Zagreb (one day to Plitvice Lakes, plus two other day trips TBD)
Thursday–Sunday: Road trip — Zagreb → Graz → Lake Bled → Ljubljana → Opatija → Zagreb (overnights in Graz, Ljubljana, and Opatija; stopping at recommended sights along the way)
Monday: Return flight from Zagreb

We realize it’s a fair bit of traveling, but we’re comfortable scaling back or tweaking the plan if needed based on conditions. Or is there anything to cut out or reconsider?

Again, thank you for all the insight so far! Very much appreciated.

Remember to let the rental place know what countries you are driving too. Also, in Slovenia you need a vignette for the motorways. You can get it online. For the tolls, you can tap your credit card.

That looks okay to me as a general start. You should look at what you want to do and the best times to do it, some shops might be shut when you are here and everything will be shut on Sundays and New Years holiday at least in Croatia. You may want to book an apartment with a kitchen for that day. This is good for Croatia as all private accommodation here is regulated by the government, and apartments are more popular than hotels, just find one you like with enough good reviews on Booking.com and it will be good. I generally stay in hotels in Austria though so do not know if that holds true for other places.

I would also be very slightly concerned about needing to get from Opatija to Zagreb if there is fresh snow due to mountains there, you may have to go via Ljubljana. It is not too important but I would reverse the travel order.

What is Zagreb food tour?

Ivan, a food tour is where you pay a fee to be taken around a city to taste their most popular or national dishes. The guide usually gives a bit of background information on each dish. In Zagreb it may include čevapčiči, sarma, or local cheeses. The tour could also include the local drink (liquor) and a dessert. The price of the tour includes the food.