Still not decided our family trip !

Have you considered the Scandinavian countries? Copenhagen gets rave reviews as a place to take kids.

I was also going to say Scandinavia and Copenhagen. Our friends lived in Copenhagen when they had small kids and loved it.

The only thing we would like to avoid is Scorching heat. We can live
with some hot days (and in july there's gonna be some of them !)

1) Round trip around Germany

In this case consider Northern Germany. The region is hardly known outside Germany, but actually the most popular summer destination of the country. Here is a map with the highlights of Germany according to Baedeker, Germanys most popular travel guide: click me.
As you can see, there's plenty to see. It's a great mix of big city (Hamburg), cute small towns (4 of them World Heritage Sites), beautiful resorts, fishermens villages, long sandy beaches, Nazi relicts, nature, and there even is a fairytale castle.

I will - of course - vote for Denmark as well, but it is an expensive place to be a tourist. You can make it cheaper by renting a house or two (e.g. http://www.novasol.us) and cook your own food. This will also make it more relaxed for the kids.

And I would also vote for Great Britain and/or Ireland. Not too scorching hot in my experience and if your kids are English speaking they can communicate with people they meet (I cannot see where you are from)

Scandinavia is beautiful but expensive.

You may find that Croatia is hot in July, but it is a fascinating country with plenty of recent history, old walled cities, great beaches and is easy to get around. It is the best value on your list. Istria will be cooler than Dubrovnik in the south, so work north. There are plenty of hill villages which are cooler. Possible day trips or a few days could be spent on an island.

I am not sure that there would be as much to interest you in Belgium and Holland.

Germany and France would give you a good mix, but are much bigger, so be selective as to how much travelling around you do with young children.

Northern Spain is the riskiest weatherwise and although it has stunning mountain scenery, it is the location I would suggest is the least suitable for young children. Southern France is expensive. You could combine northern Spain with northern Portugal. Cheaper than France. Stunning scenery.

All locations are safe.

I would choose Croatia and Bosnia. I don't know anyone who has been there that hasn't loved it.

Thanks for your suggestions, they are appreciated and give me a lot to think about ! Some thoughts:

1) Scandinavia won't make the cut this time,. It's too expensive for our budget.
2) i'm from Montreal and english, as we can see, is not my first language (french is). My kids don't speak any english.
3) we're gonna take a good look at Serbia-Croatia. For now germany seems to be the winner !

Be sure to involve your kids in the planning. They will enjoy feeling part of it, and it is a wonderful, educational experience.

To pair with Croatia you might want to check into Slovenia or Montenegro. There are so many beautiful places in all three of these countries and many sights, walks, hikes, etc. both you and your children might enjoy. Also, price wise, these are good choices. Once you've picked your destinations, I'm sure there are many suggestions we can give you.

Amsterdam - 3 nts
Paris - 5 nts
Switzerland - 6 nts
(Lausanne>>Lauterbrunnen>>Luzern)
Munich - 4 nts (day trip to Salzburg)
Vienna (or fly to Venice) - 3 nts

Another option sticking to Germany and French speaking destinations.

Paris
Alsace - Strasbourg or Colmar
Baden Baden - Rhine
Munich
Berlin
Cologne
Belgium

Thanks once again for those suggestions !

Bothmy girlfriend and I have already been to Paris. It was a long time ago (15-16 years)_ and we weren't together at that time but stilll. I personnaly already been In Alsace, Belgium (only 6 days) and Amsterdam 14 years ago. It was a long time ago but I still got wonderfull souvenirs abouit those trips ! Despites those good memories i'm more inclined to go somwhere else.

Of course we could get place with lower cost (Hungary, Romania, Bulgaria) but we are not sure that it's great place to go with young kids for the first long trip they do.

Over the past ten years we have spent a lot of time in Central and Eastern Europe and I wouldn't hesitate to take the kids ..... well except for the fact that a vacation with the kids isn't really a vacation..... Just kidding. We've taken them to Hungary and Slovakia on several occasions and if they hadn't been in school they would have gone to Romania, Bulgaria, Montenegro, Croatia with us. My 22 year old will be spending spring break in Budapest with some of her friends. And yes, they are all affordable. Locations with lots of things kids would be interested in from beaches to deep caves to high mountains to fortresses to castles to fishing and horses.

A few ideas for Budapest

http://visitbudapest.travel/guide/budapest-with-kids/
http://travelwithbender.com/travel-blog/hungary/10-things-to-do-with-kids-in-budapest-hungary

If you want to try smth new you can visit Thailand.
Last summer we stayed here http://phuket9.com/property-contract/phuket-villa-rentals, were satisfied. It is totally safe.

I thought you decided on Germany in a separate thread? If so, I would delete this thread because folks will continue to comment needlessly on a variety of options.

I forgot this thread ! yes we have buy flight for Germany for this summer. No more help is necessary, thanks to all !

Below are two links that will bring you into mild temperatures. The second link from Rick Steve's show was the inspiration for my family's trip in 2012 to Salzburg, Hitler's Eagle's Next, Lake Koningsee, Salt Mines, Lake Hallstatt, and to a B&B in Werfen Austria. My kids actually jumped on the trampoline featured in the video. Very inexpensive B&B.
https://community.ricksteves.com/travel-forum/austria/3-nights-in-hallstatt
http://www.smithsonianmag.com/videos/category/travel/salzburg-and-surroundings-rick-steves-europe/