Can I automate maintenance for paying guests?

[musicproducer]

Dear masters of the spa, I have spent days reading the threads here and thank you everyone I have learned loads.

I Have owned my spaform 4000 for 12 years here in rainy old England. it has 6 seats and a bubble bed, large twin filters, 1 x twin speed pump, 1xhigh speed pump, a light, a non functioning blower (dead blower I think). Pipes are clean, pumps and seals are new etc etc. You can fit 8 people in it comfortably and It works perfectly but is now being used by paying guests staying at the house it's at. When guests stay for more than one night the problem arises, no one is able to go there and check the tub and chlorinate etc.

Generally, most bookings involve 5-8 guests getting in drunk and dirty for a couple of hours, they crank the temperature right up and spill booze amd smoke in it and generally have a bloody good time. Fair enough. However, after the end of a stay it's sometimes inevitably a foul smelling green or cloudy beer pond.

Before each lot of guests arrive, we get the ph neutral, filters clean and chlorine to 7ppm. We add 1 x small chlorine tablet directly to the skimmer weir trap above the filters. This has usually disolved by the 2nd night.
I Keep the filters changed every week and clean up any problems after each booking but with a 4 hour changeover time between guests there will be a day when the tub isn't ready or cold for the next guests. This can not happen! Plus I don't want the chlorine dropping to zero like that.

I used to use Aquaguarde (think this then became aquafinesse) in the past and I don't mind doing it again if that is the best   solution.
So I have some questions...

1. How can I get the guests to add chlorine shock without having them handle any chemicals or do any testing.

2. Can I remotely maintain it via some cool internet based system?

3. Is aquafinesse with 2 slow release chlorine tablet dispensers the answer? I don't think 1 dispenser will cut it.

Bather load is usually high. Up to 8 people for maybe 2-3 hours.

It's currently sanitised with stabilised chlorine granules, mixed up in a jug with water then poured in slowly into the jetstream. It has an O3 generator too.

Money is the lowest concern, I have to protect my holiday home business from a bad hot tub situation and the guests can not be exposed to dangerous chemicals at all or be involved in maintenance.

Has anyone got any cool ideas?

Thank you very much for reading this, you lovely clever people.