Are two part time nannies good or bad idea?

[Bando]

My DD is 2.5 and at nursery 3 days a week. DS almost 1 and there is no space for him at nursery until August/September.
We have found another nursery but it's in completely opposite direction. We still might go with it given its a temp problem, but I've toyed with idea of using a nannyto plug gap.
We are in final stages of finding a perm 2 day a week nanny, but I'm now thinking to maybe get one in to cover the 3 days toddler at nursery so we're not running around ragged for 5 months!
Thoughts?

What are the other options?

Lets say DD goes to nursery Mon,Tue,Wed.
DD and DS have a nanny Thur, Fri.

Are you needing childcare for DS on Mon,Tue,Wed?

Can the two day nanny do any additional hours or do they have work already for three days per week?