Monty, do please send in those recommendations to the manager. They'll want feedback, and as yours is couched as recommendations, rather than sounding like a rant, they will definitely give your ideas attention. They must particularly have their attention directed to disability access to lavatories, temp or not. What you might want to suggest is that they provide a viewing dais for the wheelchair-bound, as they do at many courses (Ascot is one example), so they're not disadvantaged from seeing the finish. I doubt there's a business case for an enclosure for the old and infirm, but there is an accessibility case for a viewing dais, and perhaps some more bench seating.
As far as the very young are concerned, you could suggest that they run a creche, where parents pay a small fee, perhaps £5 a child, to park them with a qualified attendant. Unfortunately, attractions for the 'very' young have to be factored into the entry fee, as none of them are cheap to hire, due to H&S considerations.
Well worth sending them an e-mail outlining your observations, and do let them know that, overall, you had a great day out.