Hi A.,
Sleep training is just that... training! You have to be the one to determine your child's sleep needs and that includes wake-up and bed time.
You start this by establishing a routine. Wake up each morning at the same time, naps at the same time, bed-time at the same time. It also means that there is routine in getting him ready for bed. For example: a bath, turning down the blinds, brushing teeth, a good-night story, prayers, tucking in, and kisses before turning down the lights. Children love consistency and routine and the more your stick to your routine they will be happier and easier to manage. I am working on the exact same issue with my six month old. I want him to have these sleep habits developed before his sleep patterns get too established.
Please note, I do NOT take my son out of his bed once he's awake. I have him stay in his crib until I determine that his rest time is over. He has fallen back asleep almost every single time. I also leave a few small soft toys in his crib to keep him busy and quiet until wake-time. This same principle can be applied to your seven year old. Have him stay in bed until you come to get him, and give him a few toys (or even better..books) on his night stand that he can play with until you get him. Even if he doesn't sleep, he is resting and that is still beneficial to his growing body.