We have used tile (works best on a cement pad); an overlay decking that comes in squares like tile and rubber mats over painted deck.We inherited artificial turf ... didn't really care for it.  

Consider a new amenity for your rentals.......a backyard kennel, doggie playground, big bone door mats, doggies doors and walk in tubs with leash attachments!

Will put in grass erosion mats over the grass seed tomorrow. 

If they are on a term lease (I only use MTM for this reason, among others), offer to release them without penalty.You haven't given much context, but I worry that this could be a high-maintenance tenant and if you "give a mouse a cookie..." 

@Mat Deveaney, You will see over and over again, "You make your money when you buy."

In the case of emergencies the landlord mat enter without notice.

" Good and great deals are around, always, if you get out there and find them.I lose interest with Mickey Mouse in the Playhouse deals sellers can create.  

Mouse over their avatar photo then click connect in the popup.

It is called The Self Directed IRA handbook by Mat Sorensen.

California sales license is a Mickey Mouse exam.