I don't know about Level 1 Mandalas, but you can download a few free Mandala worksheets here:
http://www.shichidaparents.com/rc/mandala.htmlI've also bought Mandala worksheets from this site:
http://www.homeeducation.sg/You can download some sample worksheets to see which booklet is most suitable for your child.
How to do the Mandala activity with your child:
Show the coloured Mandala to your child for 5 seconds. Then get him to mark in the colours on an uncoloured Mandala of the same shape and see if he can remember where each colour was.
In Heguru, the third part to this activity is to reproduce the entire image. You show your child the coloured Mandala three times. Each time for 5 seconds, then removed it. Get your child to draw on a blank sheet of paper the Mandala and to mark in the colours. This part is obviously a lot harder so start with the colours first.