The horsey set in old Boston

Suffolk Downs?

Looks like they aren't planning to be on roads and this may be a rental or lesson set up.

From the looks of it, maybe the 1880s?

The terrain and house look familiar - I think I joined an organized bike ride there at some point, or maybe that is the Mass Biologic Lab in the background (pushing it to the late 1890s)?

Looks like it could be near the Jamaica pond.

...prior to harvesting it. There’s a contraption off at the far right that looks like a horse-drawn ice-cutter to me. I’d say Jamaica Pond too, since the Jamaica Plain Ice Company harvested ice there in the 1870’s. The house in the background also looks vaguely like the Perkins Estate,, Pinebank, which was demolished about 10 years ago.

This photo appears to be rotated clockwise from level by about 12°. [Determined by measuring the edges of the building, and separately, many of the trees. The average vertical slope for the trees closely matches that of the building. Also, the legs of the horses and the midsections of the people standing exhibit slopes of about the same amount (although given their relative size and the obscuring effect of clothing, this data is less clear.]

That would mean that the top of the hill is actually closer to level and the field upon which the people are arrayed is actually level/sloping very gently down to the left.

I don't know if this will help anyone make a better ID, but I figured it was worth sharing.