That will work.
Is there any concern on children around the age 5-6 attending or does Fred not want to have small children in there?
We had a discussion on that topic a couple of years ago and what they had found was that the 3 hours or so was quite long for kids to be still etc (Fred talks about the cars and their history and their past owners fairly extensively so it can be boring for kids ....). So, generally they do not recommend having small children along for that reason and also some of the cars are very, very valuable and not entirely roped off (etc.) and people should not be touching the cars (and often their original paint!).
5-6 is fairly young so it might be best to get a baby sitter etc. I am thinking but you know your kids better than me so I'll let you be a judge of that.
Really this is a tour for adults with a lot of patience and listening skills.