My advice is to try and engage these kids in a simple manner, but not underestimate their level of curiosity or understanding. In my CCD experience we were often told about the lives or experiences of certain saints and while that is well and good, I think sometimes, in the limited amount of time you have with these kids, that Jesus really needs to be cemented more so than He was at least in my experience. In knowing and loving Jesus, wanting to learn more about the lives the saints will flow naturally from that and hopefully inspire greater devotion.
Speaking from the perspective of someone who was once a 5th and 6th grade boy in CCD, I would have loved to hear more about the side of Jesus that we saw when He chased the money changers out of the temple. Yes Jesus preached love in His ministry on earth, but He was strong and resolute as well. It’s typical for young boys especially, to admire and look up to super heroes, not just super heroes, but people that stand for something, that are strong, and showing this side of Jesus, would I think resonate with young boys in particular and instill a lasting connection to Jesus in the midst of a secular culture that so often paints Jesus as being a type of hippie that is “okay” with everything, even things we profess to be sinful.