If your property is large enough to accommodate a family, I would definitely get a pack 'n play and some kids plates/utensils. 

I actually built one of these when I was a kid.

(Just kidding about the bucket, I'd make them buy their own bucket). ;-)However, if it's cosmetic,I'd just wait until they vacate.  

I want to hold commercial multifamily long term but i barely have any cash saved and now have a kid coming so I'm not sure which route to go.

Further, many (again may not be a majority, just more than another group) have life’s “out of control”; domestic violence, drive by shootings, kids with gang affiliations.  

If their kid was on a breathing machine, they would need a lot more than $600 to cover the expenses.

Lol only kidding, but seriously you can offer cash for keys but stipulate they leave the home clean, it will save you a lot of money just in labor cleaning up the place when they leave and if they leave it dirty remind them that was the stipulation.

For me I have 2 kids and a 3rd coming soon so I didn't want to spend time building my management team. 

But read up on fair housing laws, (don’t say no kids allowed) or something like that.

I was interested in buying rental units, with the hopes of maybe passing on to my kids.