We tried putting grass seed down and it hasnt taken very well at all and its purely mush underneath which is a pain as the ground is always damp and boggy like. And the trouble is there is a great big oak tree right behind our garden fence which block out alot of the sun light. I want to put something down which is going to grow or something which will be ok for the kids to go outside and play on.

I like the idea of the moss but not sure weither that would be ok or not the strip of garden is about 13ft long x 6 ft wide so not overly big but big enough.

It should be fine. Good Luck

just make sure whatever low lying plant u put in that its good for both water and shade as the tree is keeping the sun from drying out the ground around it and if u get perenials thats even better because they'll just multiply and u wont have to worry about replanting and the ground would be a lot dryer --hostas work great and the plant suz mentioned above looks great and should do the trick just fine