"How much are these points worth?" is a common question in all programs. It's a tricky thing to answer... and usually the best answer is determined by examining cash-vs-points tradeoffs at properties you'd like to stay at (or other awards you'd like to redeem for). You've got specific properties with specific rates in mind, so that makes your calculation easier.

Start by figuring the redemption rate each property offers with its points-only rate. At the Boston hotel you can save 0.975 cents per point (cpp) -- calculated as the $390 cash price divided by 40,000 points. At the SF property your value is just slightly lower, at 0.9 cpp.

I'll note here that these are both very good redemption rates. The consensus on FT is that IHG points are worth 0.6 ~ 0.7 cpp. You have an opportunity to get well above average value. On this point alone I would rule out paying cash for these properties on your dates.

Next, consider the Cash & Points (C&P) rates. The best way to think about these is that you are buying 10k points at 0.7 cpp and then redeeming at the rates figured above. Since both rates are well above 0.7 cpp it might be a good idea to choose C&P. You're essentially arbitraging the difference between 0.7cpp and 0.9~0.975cpp.

The reason I emphasize that C&P might be a good idea is that if you really want to accumulate points there are ways to do it that are cheaper than 0.7 cpp. For example, IHG periodically offers points sales with bonuses in which the price can drop below 0.6cpp (when bought in sufficient quantity, like 100k).

I would only do C&P if I anticipated more redemptions in the near future at substantially greater than 0.7cpp and needed to ensure I had points on hand for them. Since you've stated you've got no such plans, I recommend you go with the points-only options. Enjoy your trips!