Better to buy a good board 2nd hand than a bad board new. I wouldn't get those boards. That paddle on spreets is really bad.

Look on the buy/sell section of Seabreeze.

Size-wise, since you are mainly looking to paddle on flat but not surf, I'd go bigger if possible, certainly for your husband.

10'6 to 12'6 for you, and 12'6 to 14' for your husband.

^^^ what DJ said.

Hi Nix,
I'm in a similar position to you but have got our boards sorted.
We paddle in the Maroochydore river and often close to the rivermouth.
I'm 92 kgs and my wife is 55kgs then we have our 4yr old boy and 11 and 13 yr old girls.
We can get all of us on our two boards but my 11 yr old is a flea weight and 13 yr old not a big girl either.
My board is a Naish 12' gs touring which is 260 or so litres.
My wife's boar is a Fanatic fly 10' which is 160 litres.
So I can put the 4yr old and 11yr old on my board and paddle fairly comfortably if the tide isn't against me and/or I'm not paddling into a headwind.
That's when it gets more difficult.
If you're paddling when it's calm and with little or no current an overloaded or close to overloaded board can be do-able.
Paddling the big Naish is great for me in even windy conditions due to it's stability (31" wide.
I just got my self a used 12'6" race board to paddle solo just for pure speed in any conditions too.
My wife loves her Fanatic fly 10'er and she paddles it easily. When it's calm either her or my 13 yr old daughter can paddle it with both of them on board.
BUT if you are not intending on surfing the boards then for flatwater I'd be looking at used race boards because you'll find them better for handling current and adverse winds. By being able to cover more water you'll get more out of your paddling rather than having times where you might struggle to go anywhere.
Sometimes the current at the Maroochydore rivermouth is the equivalent of an aquatic
treadmill. Lots of paddling and hardly go anywhere which is no fun.
Luckily for you the Noosa river is more sheltered and God smiled on that joint when he created it.
My strong recommendation is to drop in and see the used boards at Ocean addicts opp Aldi at Maroochydore.
They've got a good selection of used race boards atm and in the price range you're looking at.
Big plus is you can take yourselves along and demo them.
We use Naish adjustable paddles and for recreational paddlers I love them.
Easy to adjust the length and I find myself altering the length while paddling depending upon whether I'm going upwind or downwind.
You're welcome to meet up and have a look at the boards we are using. PM me if you like.
That will really help you figure out which way to go.