Only 6 months to go from non-cyclist to super-long-distance-cyclist (plus mountain walker)...
If you progress steadily, that would imply being able to do a fairly hilly 150 mile bike ride (and walk up a mountain at the end of it) in 16 hours by the end of April. That sounds doable.
Being able to do it twice in 32 hours sounds like hard work to me, and that would be by the end of June!
The full challenge sounds, er,
challenging!
Good luck with it, but you are going to have to really get stuck in to be ready in time.
PS You will need to make damn sure that you are both are very comfortable on your bikes. Any little nagging discomfort after a few hours of riding would probably become unbearable after 20 or 30 hours, let alone 48.