My husband and I try to stay in B&Bs when we travel for pleasure or for work, and have probably stayed at hundreds across the US and Europe in our lifetime, so I have really strong opinions about this. You didn't ask specifically, but here are some general comments about things that have bothered me at some B&Bs:
1. The breakfast should be fresh, homecooked food (locally source food is better- probably especially true given where you are) and not just a greasy meat/egg thing and some boxed cereals.
2. I love old houses- I live in a real old one- but some people seem to think that run-down is the same as old. The bathroom can't be caked with grime in the grout, have faucets that don't work, have bedding from the 1980s, etc. Old and charming is a winner, old and run-down is a dealbreaker. Include pictures on your website that help someone tell the difference.
3. B&B owners who are polite, friendly, and have good recommendations for local restaurants/attractions are great. B&B owners who sit with you at breakfast and ask you the kind of questions your annoying, nosy sister-in-law would ask are a guarantee I would never go back.
OK, so now to your specific questions:
1) A well trained and respectful dog at the B&B
Yes, this would be fine. And, would be even better if you'd let me bring my dogs with me too.
2) Horses, and horse riding lessons, or just the ability to ride (for experienced horse people)
Since I am typically staying in a B&B while I'm on the road for work, I don't think I'd have time to fit in lessons, but would love the ability to ride if it worked with my schedule- that would definitely be a draw for me to pick this B&B over others.
3) A carriage ride to town, opposed to a taxi
Would depend on if the carriage ride was "on demand," or if I had to take it based on your schedule. I can admit I am not a patient person, particularly when I'm traveling, so I think a taxi would probably be a better fit for me. I also am not really the kind of B&B guest who enjoys socializing with other guests, so I might opt for the taxi for that reason too.
4) A Small museum on 1800's lifestyle in the guest house
I love when B&Bs have a lot of local history or artifacts from their house (the library in Shaffer Baille Mansion in Seattle is one of the best I've seen)- but if this is just a generic overview of the "1800s" that isn't tied to your specific B&B house, I wouldn't pay much attention. Would definitely not be a draw to stay at the house vs. other B&Bs.
5) A house that is decorated and built like a 1800 house.
Not sure I understand. Are you talking about building a new construction house to "look like" an 1800s house? I am personally not really a new construction person, and I suppose one thing that does draw me in to a B&B is the history/significance of the structure. Something new would probably not be as appealing if there were more authentic, interesting alternatives.
6) The ability to try sidesaddle riding from the 1800s
Probably not something that would influence me one way or the other
7) The option to rent 1800 clothing and have a photoshoot on a horse/in the historic house.
I would definitely not do this
Reminds me of a terrible Christmas when my mother insisted my brother and I take part in this kind of photo shoot for a Christmas card, and I fought tooth and nail to not have to participate.
Don't know if any of this is helpful- for whatever reason, I have strong opinions about B&Bs and do a lot of active research prior to traveling to find one that will meet my preferences.