My tenants are not allowed to take possession until they have untilities transferred.

Are these properties that you have obtained the lien/deed & have taken possession or are you just trying to generate income from leads?

I already posted a notice of abandonment weeks ago and regained possession of the house.  

There is no requirement that a specific form be used - - it can even be in handwriting.As a tenant, I would include:I will be moving on mm/ddI suggest you schedule a walk thru asapI will surrender possession on the date notedand I expect my deposit to be returned in accordance with the regulations of the State of ______.Sign, date, mail certified if there's an adverse situation like this.

I'm confused , are you asking how to help the lady out to keep the property  or how to take possession of the property and not slip through your hands ?

If you act like an owner, paying for maintenance, you have a problem if you go to court.Here are some pointers to avoid a re-characterization of a lease w option to buy being declared a "disguised installment sale"Here’s what the IRS looks for in determining whether there has been a sale:(1) Whether the amount of and right to the purchase price is fixed and unqualified;(2) Whether the obligation to convey title on final payment of the purchase price is absolute;(3) Whether the vendee has taken possession or has the legal right to possession;(4) Whether the vendee has otherwise assumed the benefits and burdens of ownership.

I have not done this, and as you will see I am a new investor, but I do possess knowledge in this area.

If the possessions is given up earlier, then the 21 day time clock starts when the landlord gets possession. 

My kids grew up fine in rooms that were 10'6" x 9'11" and they had room for all their worldly possessions, a bed, a dresser etc. 

Give the tenants back their possessions in accordance with the law for your jurisdiction.