That's alright! It's not about how experienced you are... it's more about the spirit of exploration!
[Just the idea of getting to see what the tunnels hold and where they lead is enough to get him excited about the prospect, despite not knowing where everyone else is... but if everything goes well, they'll run into them along the way!]
Besides, you said you'd like to explore ruins around the world, right? These aren't exactly ruins, but you have to start somewhere! We'll find the others by finding our way out of here, too, so it's a good course of action.