Apart from our day tour of the Yorkshire Dales, are there any sights for which it is recommended to book ahead in York (in August)? We plan to do the castle museum, the Viking museum, the chocolate museum, a river cruise, walk the wall and the Shambles area. Am I missing anything? Thanks in advance.

Nothing really needs pre-booking -- except if you want to take one of the 'Hidden Minster' tours of the Crypts, or masonry or Chapter House.

You won't see all of the Dales on a day tour, it depends on where the tour takes you to judge. As janisj says, don't miss the Minster and a tour of some of the old historic pubs in the centre of the old part of town. There's also the Railway Museum if you have any interest in old steam trains.

https://www.yorkshiredales.org.uk/ big place, where does the tour go and have you looked at alternatives?

Merchant Adventurers house not that exciting but a good story and building https://www.merchantshallyork.org/

I was going to mention the Railway Museum too - brilliant place and much more than just steam trains!

@ Morgana: Thanks! Yes, we're staying not far from this and hope to visit on our first afternoon.

We're doing this tour...Yorkshire Dales NP and All Creatures Great and Small Filming sites (might be touristy, but I'm a fan). I looked around a bit, and this suited our interests and budget.
https://bobholidays.com/tours/herriot/

I saw tonight on our local news that they are starting to record the next series of All Creatures in Grassington. Not sure if this link will work for you.

All Creatures Great and Small village Grassington taken back in time - BBC News

It looks a pretty decent tour - some interesting places and not trying to do too much. And you practically go past my house!