The agent P adventures are a lot of fun. DD(6), loved them on our trip about a month ago. I think DH enjoyed them as much as she did. They are available in several countries. Each country takes around 20-30 minutes, depending on how fast you find the places you are supposed to go for your mission. You can do one country, or all of them. We wound up doing all of them over the course of 2 days, because DD really loved them. Last year when they had the Kim Possible missions, we only did 2 because I told DD she should save some for the next trip, and when they replaced Kim Possible with Perry she was a little irritated that she didn't get to do the rest of those, so she was determined to do every one of the Perry this year.
What is really neat is that you get to certain locations where the phone leads you to, and then when you push the button on the phone certain things happen at that location. I don't want to spoil any of it for you, but some of them are really neat. For anyone wondering if they are the same as the Kim Possible events, there are definitely some new things that have been added. The week we were there, the CM told us that they had just added a couple of new ones within the last week or two as well, and they might not be done yet.
I think your son will love it. The 5 year old might like it too. DD, really enjoyed the Kim Possible when she was 5, although she needed more help that year.
It is definitely worth at least trying one country. If you don't like it, you don't have to do any more countries, and you could even quit and not finish the mission if you really didn't think it was any fun.