I can't speak to the Devils side of this, though I'd be surprised if they took Graves back.
As a Kraken fan you've definitely got me tempted by our side of this deal. I think Ottavainen projects 3rd pair and may be ready to step up to NHL as soon as next season. Brief dig suggests Kangas has similar potential, just a few years behind in the development curve. The 3rd not being until 26 is a bit painful though, ideally want something sooner than that, like your 25 3rd. Or if we are going to wait to 26 then your 2nd round pick instead.
On balance I think if teh pick was tweaked I'd take it. We can pick up a veteran 3rd pair RHD in UFA for not a lot.