His birthday

Okay ladies I’m trying to plan this surprise birthday dinner for my bf and his sisters aren’t helping.. he’s expressed how he’d love for them to be part of his day. So I’ve texted both of them so I can RSVP and both asked for details and nothing more. His birthday is this Friday, I just texted them again this morning and nothing. I recently met them and they were both nice to me so I don’t understand what’s going on. I don’t know how to handle this.. it was suppose to be a surprise where they meet us there.

One left me on “seen” the other just nothing what so ever..

What do I do now?