Need Advice for Concrete Walkway/Driveway Upgrade

[James Are]

I have a property in Tacoma, WA with two houses separated by fencing. Parking for the second house is behind the garage and is not enclosed by a fence (see photo). The pathway from the second house to the parking area is a big mud pit. I bought the house late last year and have been watching for a four to five day window of good weather to add a concrete driveway and walkway to the home. The current tenants (2 adults, 3 small kids) moved in late January and will vacate and the end of April (previous tenant broke lease; these tenants are paying $250/month extra for short term lease). They’ve politely inquired about the walkway but have been patient. I’d like to start the project next week. All together it will cost me about $7k. I am NOT looking to pass this cost along to the tenant so I’d love to hear ideas/suggestions to be sure that their kids don’t ruin it before it can fully set. I will charge them if they damage it but would really, really prefer to minimize the chance of that happening. I don’t have any security cameras on site and would prefer not to have them there long-term but perhaps it makes sense to have a camera short term in case someone damages the drying concrete? Should I have them sign something that gives their permission to proceed? Any ideas or suggestions would be appreciated. I will let the three adult tenants in the other home know about the project but they’re unlikely to accidentally cause 

damage since their house is separated by a fence.