Some people like the riverboat, but for me, it was kind of boring, and I haven't wanted to go again... You just go on a loop around Tom Sawyer island, you see some very artificial scenes and end up where you started. I didn't find it interesting or fun, but I know others do. If you want a boat ride, the one from parking to the MK gives another option!
Tom Sawyer Island is basically one of the coolest playgrounds ever. Your 13 year old might be a little on the older side to really enjoy it, but lots of kids (and even some adults...) will have fun running around, exploring tunnels and caves and a fort and the barrel bridges, etc. The thing about this one is that it eats up time. You have to wait for a raft to the island, then spend however long exploring the island, then when you are done, you have to wait for a raft ride back. Careful about when you try to go, since if you are there when the island is crowded, and you are trying to get off the island at a time others are, you could end up waiting a while for multiple rafts to shuttle you back and forth. If you are in any kind of a rush, it can be annoying to be "done" and have to wait a while to get on to the next thing. However, if you have the time and can go at a more leisurely pace, it can be interesting. If I remember, they close this one near dusk, so you can't do it late in the day.