Transferring trial site to client with active subscription

I've just finished building a trial site that is ready to handover to my client. They have an existing live Squarespace website that this new website is meant to replace. Can anyone assist in how to go about transferring this to the client, and then assisting them in taking their current site offline and making the new site live? 

Worth noting that the client's domain is hosted on GoDaddy

This is what I would do:

1. Give the client Administrator access to the new site
2. Get the client to subscribe to the relevant plan on the new site
3. Make sure you've added in all the URL redirects and SEO content to the new site
4. Password protect the old site 
5. Disconnect the domain from the old website 
6. Add the domain to the new website
7. Update the verification CNAME record for the new site in the GoDaddy DNS (or as it's GoDaddy it may give you a popup with the option to add records automatically)
8. Once the domain is fully connected, publish the new site
9. Cancel the subscription for the old site (or tell the client to do this)
10. If the client was paying annually for the old site, message customer care with the built-in domains for both sites and ask for a pro-rated refund for the old site because you upgraded/transferred to the new site
11. Optionally transfer ownership to the client (but only once they have paid you)!

Let me know if you have any more questions about any of these steps, I know a lot of seasoned developers who still hate doing domain switchovers but in this case most of the records will already be correct so it should be pretty straightforward. 

Thanks for the response Katy! This is one topic that I do find difficult.