I am planning next year's summer holiday and want to take the DCs abroad for the first time. I'm looking somewhere with a nice beach and places to explore. Ideally we would like some sort of self-catering package option if possible.
Lovely choice to have! Haven't visited Croatia but DP and I are off to Slovenia this summer - very excited as it's meant to be a fab place, but it has a very short coastline so if it's beaches you're after you're likely to have much more choice in Croatia. Our holiday is likely to be more outdoorsy/cultural than beachy -we're doing a week in the Soca Valley near Bovec, and a few days in Ljubljana (visiting Lake Bled, caves etc from there). Apparently there are a few nice beach resorts though - I've heard that Piran is lovely. Not sure about package options as we're travelling independently.
Slovenia is fab fab fab but it has very little coast. The best bits of Slovenia are the mountains. Bled and area around there. If you want the beach I think Croatia has more options. We did go to the Slovenian coast but it was more of a one-day visit, not great for staying.
We have been to The Istrian part of Croatia for the past couple of years. The beaches are not beaches as such but very rocky and stony. It makes the water clear and great for snorkelling - my teens love it but not suitable for young children as there is often nowhere to paddle.
You are in luck as self-catering is 90% of what Croatia does!
There are not many sandy beaches in Croatia. The authorities cover the beaches with gravel at the start of the season to keep it topped up. (Croats are very proud of their non-sandy beaches).
Slovenia is like Austria-lite. It has some lovely spa parks that are a fraction of the price of the Austrian ones, but also not quite as modern. Lake Bled is lovely. Ljubljana is definitly worth a day's visit.
However, Croatia is the place for beaches. Sounds obvious, but it gets warmer the further south you go. What about somewhere near Primosten (which has a lovely beach for young children)? Or one of the islands. Brac?