Wa `alaykum as-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- In summer time, all members of the family should try their best to help one another lead a sin-free and enjoyable life.
2- This can be achieved by staying away from all sources of temptations that affect one’s behavior negatively.
3- In addition, one must strike a balance between one’s religious duties and enjoying summer in order to remain attached to one’s religion and safe from moral decline.
In his response to your question, Sheikh Muhammad Al-Mukhtar Ash-Shinqiti, Professor of Political Ethics and Religions History at Qatar University, states:
You need to get in touch with some Islamic centers and youth organizations that usually have good programs that combine both fun and education at the same time. To give you some good suggestions, I could list the following:
1- If you can afford it, you may take your family for `Umrah or a visit to a Muslim country to see the Islamic historic sites.
2- You may take your older children to study Arabic at some Islamic or Arab countries. There are plenty of Islamic centers that particularly work in that field.
3- You may take your family to enjoy the summer at other places such as mountains or any other place that is enjoyable. I do not recommend you to go to beaches in the summer.
4- You may arrange with some Muslim families or friends to go to the park and do some barbecue where children can have fun at the same time.
Allah Almighty knows best.