what does it mean?
“The band’s popular. That’s why we got here early enough to grab a table. Did you get your power back on and everything?”
“Yeah.”
Maureen gave his hand a reassuring pat. “I didn’t have much time to talk to Abra today, but she said somebody’d been digging down in the basement.”
“Yeah, what’s that about?” Mike leaned forward. “Unless you want it to all go away for a couple hours.”
“No, it’s okay.” In any case Bluff House was a key part of the com-munity. Everyone would want to know. He gave them the basic run-down, then shrugged. “My best guess is treasure hunter.”
“Told you!” Maureen slapped her husband on the arm. “That’s what I said, and Mike’s all poo-poo. He has no fantasy gene.” 】

what does "unless you want it to all go away" mean?2. what does "Mike’s all poo-poo"mean?

Question

what does it mean?
“The band’s popular. That’s why we got here early enough to grab a table. Did you get your power back on and everything?” 
“Yeah.” 
Maureen gave his hand a reassuring pat. “I didn’t have much time to talk to Abra today, but she said somebody’d been digging down in the basement.” 
“Yeah, what’s that about?” Mike leaned forward. “Unless you want it to all go away for a couple hours.” 
“No, it’s okay.” In any case Bluff House was a key part of the com-munity. Everyone would want to know. He gave them the basic run-down, then shrugged. “My best guess is treasure hunter.” 
“Told you!” Maureen slapped her husband on the arm. “That’s what I said, and Mike’s all poo-poo. He has no fantasy gene.” 】

what does "unless you want it to all go away" mean?2. what does "Mike’s all poo-poo"mean?

Answer

I'm not sure about your first question, I'm a little lost on the context of what he is suggesting to go away.

But as for "Mike's all poo-poo", she is basically saying that Mike is no fun. At least this is what I'm getting..

Answer

It's a little tough to guess from this limited context, but I think when Mike says, "Unless you want it all to go away," he's basically trying to say that the speaker doesn't have to talk about "digging in the basement."  The speaker can choose not to talk about something that's bugging him, and they can talk about other things.  Or maybe Mike is offering a distraction from the whole thing?  (like, getting drunk?)

As far as "Mike's all poo-poo," it just means that Mike is "pooh-poohing" the idea, when means he's dismissing the idea as ridiculous.

Hope this helps!