120 Litres is the traditional size of a shopping trolley
Like not a stupid giant one but not a pissy little one either.
Rear panniers are traditionally 20 litres each
front 12.5l each
A large wald basket is 20l. The basket can be loaded above the top of it, so it's more like 30l
So your touring bags hold 65 litres
And front and rear baskets will hold another 60.
You can have both, that is more than an entire large shopping trolley full of groceries. It just requires some nice racks, a real touring frame, strong wheels (bicycle wheels are frequently built to spec to carry two riders on tandems, a similiar high weight demand), low enough gearing if there are hills, and a good rider.
It is actually not that hard to ride a loaded bicycle.
The only thing really that makes this unviable is if you are an alcoholic, and lazy, and your children only drink pepsi, milk or juice.
