Blocked vs Reserved

I had some dates blocked for my son and his girlfriend. I read that blocked dates count against you in the rankings. So I turned instant book off and unblocked one weekend. Before my son could reserve it on his account, someone else requested to book it. I replied that these dates were not available as my son had these dates reserved.

It appears that all the other listings available for that date are ridiculously expensive so I doubt the guest will choose another place.

The end result is this request to book is waiting to be accepted or declined. The system says to respond or risk my response rate.

I already responded but how bad will letting this request expire hurt my response rate? I will ask my guest to cancel the request but he is probably mad because my place had a cheap rate (for my son).