Last day of school.

Today was the last day of the school year. Davis isn't too excited because he starts summer school on Monday. He will go for one week have two weeks off, go for one week have one week off then he will have two more weeks of summer school and have about a month off till he starts the new year as a 10th grader.
I tried to get Davis to celebrate his last day as a 9th grader but he didn't want to do anything with me (which is understandable). He called and called friends to get someone to hang out with, but no one would or could. I saw his frustration in wanting and trying to hang out with friends and finding no one (and on other days for that matter). So, eventually I got him to go to a few garage sales (which he loves to go to) and then I took him to Taco Bell (which is precisely where he wanted to go to lunch). He didn't want to go to a movie, or a park, or the canyon or anywhere else. I can tell this summer is going to be tough.
Our summers used to be full of fun filled activities, house full of kids, going to the library, going to parks, going to the pool, going many different places and being home enough for some calmness, playing with friends or at least some respite before our next adventure. But as Davis gets older and with the other kids moving out and onward, he wants to go out less and less. He has much less tolerance for being spontaneous and going places, with or without lots of people. He much prefers staying in much of the time. I find myself having to readjust more and more to keep Davis happy and healthy.
He's going to have field trips every Monday and Friday of summer school but has stated some apprehension about going and has asked if I could go with him (even though he is almost 16). I'm not going. He has a hard time going different places even with us.
How do I help him?
I plan to take him to American Fork canyon quite a few times to pan for gold (which is something he loves to do, but is a long drive away so we can't go frequently). I plan to get him together with one of his cousins (who is about 5 years younger than him) who he likes to hang out with. I plan to have a few projects for me to do so that if he just wants to stay home I can have something to do other than laundry or cleaning the house. I plan on working in the garden. I plan on reading some good books. I plan on coaxing Davis to get out as much as he or we can. I plan to get him his fishing license which is something he has loved to do in the past and it gets me outside (which I love to do) or he can fish with friends. I plan on having his friends over or have them come with us, if and when they can. He can go over and play with friends if he could or would. I plan to be flexible, patient and understanding and I know that it's not always that easy but somehow, this summer is going to happen and be good for the both of us.