That sounds fine but maybe a little too stiff and formal. Who uses “Dear” in this context? I’m also a little confused by “we usually leave around 10” said by them and your plan to arrive by 10 so I might want to remind them of the details of your arrival time to make sure you will be meeting before they leave! Did you guys discuss the handover in your chat?
Are you communicating through the THS message system or text or whatsapp?
In your shoes, I’d have a different ask:
Hi ____. Unfortunately, it’s not possible for us to come a day earlier than originally agreed. But I 100% agree a print out would be useful and it would be great for you to have a chance to show us stuff like the garage/key. We understand the Welcome Guide format is daunting, but it would be super-useful for us have some kind of written instructions in a google doc, pdf, etc especially regarding pet care and feeding and important housecare concerns. We’d welcome photos or videos to show us some of the stuff you think might be tricky like remotes. Would it be possible for you to send us the printout or whatever you have over [WhatsApp], [email] [whatever you used for the video chat] ? Then once we have a look, we’d love to meet for another video chat to go over any questions or concerns. Maybe you could even do a walkthrough phone/video housetour the same as you would if we got there a day early? We’d be fine with a live remote demo since coming the day before isn’t possible and the day of may be rushed.
In our experience, it’s always better to arrive prepared, rather than have a rushed handover with us tired from travel and you eager to get on the road.