Hi !
what would be the best for a family with kids of 7 and 11 years old who love history, good food, natural wonders, pools and beaches ? We dont have time to do both.

Thanks !

Dalmatia for the reasons you listed. Plus Dalmatia is a large area, while Istria is smaller, a peninsula.

You can find those things in both. I think a lot would depend on flight options and your comfort level driving (not necessary in Dalmatia, but needed for Istrian interior).

Our first visit to Croatia was to Istria, which we really enjoyed. The 2 young men who worked at our hotel told us we had to return to Croatia to visit Dalmatia, because it was the most beautiful part of Croatia. We returned this past September, and as much as we liked Istria, we liked Dalmatia even more.

Its all about what you like and when you do it.
Istria is destination that is ready to give you good experience even out of season, Dalmatia is not yet there.
About the nature '- not to be discussed as it is subjective

Istria and the Dalmatian Coast are incredibly different in their natural features, cultural legacies, cuisines, architecture, etc.

Istria was part of Italy until WWII; after the war, many parts of the peninsula – particularly the inland hilltowns -- were abandoned. Some of those regions have only recently “come back to life” as it were, largely because of artist communities and tourism. A few coastal cities remained vibrant throughout this time.

The Dalmatian Coast was a major competitor of Venice during the height of their dominance of the seas and trade, and many parts (Dubrovnik in particular) bear the marks of tremendous wealth during the Renaissance -- and along with wealth and the need to protect trade, grand architecture and defensive formations.

I would encourage you to consult a few good guidebooks, particularly those with high quality photographs.

Kja, so you are saying that Dalmatia is better ? So 3 for Dalamatia, 1 for Istria and 1 who said both are fine !

No. I said they are different. Period.

Yorkshire and kja said it best: you can find what you like in both areas, though both areas are different. Guidebooks and online research will be your friend in making this decision.

For whatever value it might hold, I will share our experiences.

We (DH, I and our then 15 year old DD) based at a resort in Umag, Croatia and took day outings to Koper, Piran, and Trieste. We did not visit during beach weather (late April) but our resort had a lovely, lovely beach. Our dining (almost entirely seafood) was spectacular at every turn. Koper and Piran were fun to explore, especially walking along the beach in Piran.

DH and I recently returned from our third long weekend in Trieste (we have friends who live there); this time the little village of Muggia amused us for an hour before sitting for an excellent lunch at the fish agristourismo on the harbor, and we spent the better part of another day hiking the Rilke Weg on the cliffs near Duino (the lookout spots are remnants from WWII). There is a castle to explore, and below the cliffs we could see gorgeous beaches. We have also wandered the trails around Miramare on a previous visit. Plus, there is a grand cave nearby, and you are within striking distance of the Lippizaner Farm in Lipica, Slovenia. Our dining in Trieste is always spectacular.

For Dalmatia I can only write that DH and I spent several days based in Dubrovnik, one of which was spent on a day trip to Montenegro (Kotor and Perast), and a half-day more or less hiking about Lokrum Island. The entire holiday was filled with everything that is a priority for you: hiking, history, good food, nature, pools, and beaches.

Good Luck!

can you indicate, a scorecard - what you expect.
if is food (than Istria)
if is nature (than depends)
if is climbing/hiking (than Dalmatia)
if is wine/olives (than Istria)
so on and so for...

Interesting! I'd have said that the food is a tie and that Istria would win on climbing / hiking. Vive la difference!