I empathize with the apparent "lack of emotion". My father and mother in law sprung for a trip to Japan for my husband and I as a wedding gift, and I was so shocked and excited because I couldn't believe it was true that I didn't have it on my face.
FIL thought I was disappointed because I didn't squeal and jump around like someone on The Price is Right. It was my wedding night, I was already overstimulated from that.
I have to pretend to be stupidly excited for things so people don't get the wrong idea...