Congratulations on the impending arrival
Do you know what "make" it is yet ?
I know you want to avoid the parking lot syndrome but actually having both types available especially whilst you need to drive instead of bike might work out better in the medium to long term but its marginal. You may get better FE with the extra use you will be making of the car and the types of trips but you lose on the expense of upkeep, tax, insurance etc.
Its a difficult one to decide because the amount of upkeep is impossible to predict even with a brand new car.
Do you have the ability to transfer tax and/or insurance only to the car you are using at the time ?