As another poster has mentioned, traversing the locks and mooring and tying off are the tricky bits.
Sure footing, quick reactions, strong hands and a cool head are all necessary if things get tricky.
If you do things by the book on navigation you should be okay, but we saw a big cruiser being towed for repairs with half the reed bed wrapped around the propellers.
Its easy to misunderstand the situation on the water and what you should do to not make matters worse - revving the engines when you're already in the reeds would not be a good idea.
We've been on the Shannon twice, once as honeymooners and once again more recently with the family.
An eight year old can safely pilot a small craft, and when the weather is fine its relatively easy.
But even crossing the Lough at Portumna can be tricky if there's a bit of a squal in the middle of the lake and you're in a flat-bottomed 27-footer.
So yes, I think the advice of getting a younger family member would be ideal, assuming they are not clueless about water.
ONQ