"Why don't we start small, and decide from there?" Ianto suggests gently. Jack he isn't worried about; it's an adventure off to unknown worlds and when has he ever been able to resist that? Spike's reluctance is expected as well but he can't help remembering that conversation they had about forever, the one they both meant. He isn't going to walk away from a future that might hold that for them.
"You'll be needing your soul back. We can help accomplish that the right way this time and then decide where we go. We don't have to plan our whole future at once."