Campn- I know what my knee-jerk reaction would be, and if it were me, DH would hear it immediately. I think it's presumptuous of your in-laws to make a decision like that, but if after hearing it, the idea grows on you, then it's one less battle in a life-time of in-laws. I would probably get upset and tell DH, and then sleep on it and see how I felt in the morning.
This from a woman whose mother, after having a whole conversation about how I don't want to use non-biodegradable diapers, gave me a huge box of Pampers at my baby shower. Of course, I couldn't say anything without sounding like a jerk in front of a room of guests. We returned them, but I didn't say anything to my mom.