Why 6 seats?
How many of your flights will be with 4 on board?
Are two of the four children?
With aircraft (just as with cars) you pay for the extra seats (greater x-sectional area and cabin length) with wasted avgas.
Singles are expensive enough to operate in Europe, the economics of ownership mean that even in the USA avgas twins have had their day.
Think Mooney Ovation.
SB