Can anyone recommend a design?

I want to build a boat my wife and I can row with our whole family aboard.
It is a large family - 2 adults, 5 children (ranging from new-born twins to
8 years) and 2 dogs of 20kg each. So we need a rowing boat carrying almost
300kg of biomass plus lunch, drinks, spare clothes, towels, rain coats,
toys, outboard, first aid kit, flares, fuel, sun umbrellas, anchor, chain,
etc, etc ... That is a lot of weight but it is also a lot of feet, knees,
elbows and paws - which add up to a lot of space.

It will be a ply sharpie. I like the flat bottom for initial stability and
the ability to put a window in it (I have visions of the toddlers peering
delightedly through it at the teaming marine life below. I like the
relatively narrow waterline for efficient rowing and the avoidance of
excessive heal induced by beam seas. I like the single side-plank for ease
of construction. We don't plan to be out in bad weather but getting caught
happens to the best. The boat needs to be able to handle estuary and
coastal conditions.

John Welsford's Mollyhawk
(http://www.jwboatdesigns.co.nz/plans...index.htm#mlhk) is attractive
but, I suspect a bit small. I have Carlson's design software and could
build a boat from the offsets it produces and would do if I felt capable of
getting the design compromises right. In particular the compromise of
initial stability vs excessive, sudden wave-induced heal vs efficiency under
oars needs an experienced designer's eye to my thinking and I have never
built a boat to my own design before. John thought his Walkabout design
would be perfect and he is probably right. However, the multichine
construction is more complex than I have in mind. Furthermore, as a decked
sailing and rowing design the plans are more complex (and therefore
expensive) than I need. It seams a pity to pay for the design of a
sophisticated camp-cruiser then build it without decks, centrecase, rig,
tent etc. etc.

So I am open to suggestions for a basic flat-bottomed, single sideplank
rowing sharpie, probably about 20' long.

Paul.