I just wanted to know if he could deliver. I

Since both proof of delivery and the date of delivery are important, I don't think this method is very good.What method do you other landlords use?

I wouldn't say the delivery drivers carry a full tool box, but they are quick and they get it there without alot of damages.

Get receipt for delivery by deadline date.

To be honest, pizza delivery guys often make more than Uber drivers depending on the location, and you can do that in any car you want. 

Paragraph 14B(3) of the California Residential Purchase Agreement says "...However, if any report, disclosure or information for which Seller is responsible is not Delivered within the time specified in paragraph 14A, then Buyer has 5(or__) Days After Delivery of any such items, or the time specified in paragraph 14B(1), whichever is later, to Deliver to Seller a removal of the applicable contingency or cancellation of this Agreement.If you cancelled within this time frame there's nothing more to talk about, the contract is cancelled. 

And whenever the Code requires you to give notice to someone, always opt for CMRRR (certified mail) and hand delivery if you can.

In most states you still need to send them a accounting statement for the deposit to their last known good address get delivery confirmation from the post office, even if they don't get anything back.

If you are going to mail check with the post office on what is the LIGHTEST LOAD mail delivery days of the week?

Conditions Precedent: The obligation of the Purchaser to purchase the Property will be subject to satisfaction or written waiver by the Purchaser of the following conditions within 60 days after execution and delivery of the Agreement.