I would go for it. I'd be more worried about a cintiq on a table because you can't really put it away when you're not using it. Whereas the ipad you can kinda stuff in a bag.
I haven't noticed any build quality issues, and so far my iPad it still purring along happily.
-Don't bother buying extra nibs for the pencil. I have yet to even consider replacing mine after 2 years of steady sketching.
If you're worried about device destroying incidents due to toddler death hugs, then there's a couple of options open to you:
-Buy a life-proof case (or whatever they're called). You can buy a pricey but tough as nails iPad case that should handle most if not all 'accidents' your kids have with your precious drawing tool.
-Buy apple care when you buy the iPad. It's expensive, but they'll cover up to two incidents of 'accidental damage'.
Also, I think with the announcement of the new iPad you can get refurbished last gen iPad pros pretty cheap (comparatively).
Regarding wacom knock-offs I've tried once and had a bad experience. Lots of issues. Cintiqs are industry standard for a reason. Though maybe things have gotten better since I tried...
Either way, good luck! Dropping that much money on an iPad can be scary.