I don't buy into the "must keep them academically involved all summer long" mantra. I mean, yes, they will forget a few things if they do absolutely nothing, but summer is SUMMER. They suffer burnout if they are still doing school all summer.
My kids are 11 and 14 and my 14 yr old is registered for AP and Honors classes when he starts back in a few weeks. Most of them have summer reading requirements. So he is doing that. But they do lots of "other" stuff over the summer that I find just as important:
* 7 day church camp that has 3 classes a day on the theological level of practically being at seminary (all taught by seminary trained pastors who are knowledgeable and can translate both greek and hebrew), which also gives them daily physical activity in the mountains--swimming, rock slides, hiking, canoeing, and playing "war" games like "Outpost". They come home exhausted physically and mentally, but they LOVE it.
* Both kids are having orthodontic work done (my 14 yr old's is major-- braces plus a herbst device), so there is growth in maturity just in dealing with all that.
* They roller blade, ripstik, ride electric scooters, and swim regularly--fresh air and sunshine!
* We have vacationed as a family (waterpark/overnight trip--loads of fun)
* They have competed in a martial arts tournament
* They maintain their martial arts over the summer-it is a year round sport. And for my 14 yr old (who is 2nd Dan) this includes progressing towards his next degree, which means devising his own one-step routines, and planning his own 6 board board break and perfecting it, plus mentoring younger students, helping in lower ranked belts classes, etc.
* They are leading the games for the younger kids at VBS
And yeah... they play games on the computer (mostly minecraft) and PS3. They're kids. They also do chores like mowing the yard, helping with laundry, etc. And we have had numerous family guests stay with us over the summer, and we play board games (like Settlers of Catan), along with hitting the beach, etc.
Just learning personal responsibility (which is a long-term growth thing, not something they can learn all at once) is a huge deal. They have learned a lot of that this summer, particularly with the orthodontics stuff and camp. They also have summer birthdays, so they have used their money management skills a lot, with birthday money, etc.
Maybe I will regret not making my son practice his algebra, but I doubt it.