My Bro & SIL have this exact same arrangement, except my mum has the baby on the day they are both working. It seems to work out fine for them, they are earning slightly more than 1 full time wage ( my brother is still at uni, but gets paid to take tutorials). My Niece is in her own environment 5 days a week, and she gets to spend equal amount of time with both her mum and her dad. If it is a situation that can work for you then I say go for it, it can only be of benifit to your daughter.