Learning about the planets, moons, stars and the sun can be a lot of fun for young kids. The trick of course, is to be creative. Doing it right can enable a child to learn quickly without forgetting later. Look through pictures online, practice saying the name of the planets again and again since most of the names will be new to young kids.
Further there are fun little activities you can do, like making a chart with little different coloured clay to make a model or little mobile cut outs that you can hang from a paper plate.
These will also help in bonding with the child not to mention that whilst doing the activity, you can pretty much discuss more in depth facts (like the number of moons a planet may have or the role of the sun etc.) and the kids will enjoy learning. Click here for a fun worksheet.
As for incorporating a little of our deen: The primary thing is to teach them that He created the heavens and the earth and He who keeps them in their orbit through gravity- plain and simple.