I have a pretty easy answer, and then a more complicated one.

The pretty easy one is to use the Skymiles for coach tickets to Hawaii. For starters, the reviews say Delta FC to Hawaii is really not worth it. If you need to move to SkySaver FC to get availability, I guess that's okay. Otherwise if you could get SS coach I'd do that.

The 8.8c/m rate for int'l J basically just takes the cost of that ticket, and divides by the number of Skymiles. However, that's only valid if you'd actually pay that much. You said here you'd pay $630 for MCO-HNL tix, if you can get them as coach saver awards then you do have a real redemption rate of 2.1c/m.
What other ticket would you pay for that will get you that rate? For coach awards to Europe, at 50k/tic that is $1050, do you see yourself spending that much for a ticket to Europe? Wouldn't make sense now when flights when some flights Europe are in the $3xx range.
I think the 2c/m valuation is a valid one if you can get that for real tickets you'd otherwise buy, which is the case. Delta is the only carrier that offers 30k awards to Hawaii (most others 35k), another reason I think to take it.

The more complicated answer involves among other things, what you plan on doing with your miles. For example, both myself and my girlfriend have 80k+ miles with United, so we easily could use 35k for a United award to Hawaii (forgetting that I could redeem 35k Skymiles for a United Hawaii award). However, one of the things I want to save them for is Australia (60k in coach, think 90k in Business or FC). These tickets easily run $1500 from the East Coast, so definitely makes sense (for me) to 'reserve' them for for that trip.

As also pointed out, you need to figure out how many miles you'd be losing if you paid for the ticket. Again, I think redeeming is the better choice. You could easily earn 10k or so with a mileage run to Europe. I'm looking at a PHL-ATL-AMS trip for end of May, return in June for $333, 10k flight miles, plus 1k for online booking. Much better 'buy' rate then your $630 MCO-HNL flight (of course your mileage runs will vary from MCO).

So my recommendation is try to redeem the miles for a coach award. Even if you need to shift to United for better availability, 35k miles for a $600+ ticket is still a good deal.

Jeff