For your older son, Boys’ Quest is good. http://www.funforkidzmagazines.com. Your daughter may be old enough for their girl mag, Hopscotch. It’s billed as being for 8 and up. Samples available on the website. What I like about them is that they are ad free and do not accept content about fashion, celebrities, boy/girl relationships, that sort of thing. They also have an activity magazine for both boys and girls, Fun for Kidz, that comes out the months that BQ and Hopscotch don’t.
Focus on the Family also has a jr. version of Clubhouse for ages 4-8.
You may also want to look at the Cricket family of magazines http://www.cricketmag.com or the magazines published by Children’s Better Health Institute. Your youngers may like Turtle or Humpty Dumpty. http://www.uskidsmags.com