Yes, you can start making skins for the texture pack. But make them as realistic as you can!

If you want to make a child friendly texture pack, start really simple and use like 2-5 colors. When it's done, add some shading. Darker colors here and lighter colors there. Then if you want, start making some great details. But if you want it child friendly, dont make the mobs all bloody and scary and stuff like that. Make them happy and cute. I think your question was a little hard, but this is my best answer. Aound by the way, I'm going to fully re-texture my SmoothCraft. If you need more help, let me know!

To make a texture pack, you need Winrar or 7-zip. You make a new folder in your desktop and go to your minecraft.jar. Then, copy the following files from minecraft.jar into the new folder: achievement, armor, art, environment, gui, item, misc, mob, textures, title, pack.png, pack.txt and particles.png. Then, you need Paint.net or Photoshop. Open the files and edit the images with your picture editor program. It is a little hard in the beginning, but when you get the hang of it, it's easy. The SmoothCraft pack was just a test, so I made it so simple. I will make better packs in the future like Slender: The Arrival 64x64 texture pack. I hope this helped, and if you have more questions, let me know!

I love this skin! It's hilarious!