There's no reason to expect that your decisions would affect the next Boltzmann brain in the sequence, so there's still no need to put value of the Boltzmann brains' decisions. I don't think it makes sense to put more weight on the specific series of Boltzmann brains where the decisions seem to be followed by a subsequent Boltzmann brain than on the much more likely series of Boltzmann brains that just resemble your mental state but don't have any seemingly-causal relationships between each other.

If you're allowed to put more weight on specific extremely-improbable sequences of Boltzmann brains, then you can propose all sorts of nonsense scenarios like "Imagine the series of Boltzmann brains where if one thinks of a purple elephant, then the next Boltzmann brain experiences the subsequent thought but also a lot of pain. Should you avoid thinking of purple elephants because of the fact this unordered sequence will happen eventually in an infinite universe?".

I think in order to really reason about this sort of thing, you need to start considering theories of the universe like UDASSA (https://news.ycombinator.com/item?id=20119513, http://fennetic.net/irc/finney.org/~hal/udassa/), which provides a framework for how we should expect to anticipate different events, and Boltzmann brains and especially specifically-selected sequences of Boltzmann brains have so little measure compared to other things including our human selves that they're not worth considering, even if their decisions actually did have a causal effect on some part of a world (which would also have minuscule measure compared to ours).