You may not have enough time, sorry.
We ate at Sci-fi at 6:30p and we were hoping to catch the 8:00p Fantasmic. Well, we were still finishing up our meal at 8:00p.
They didn't seat us right at 6:30p, I think it might have been closer to 7:00p and that's after we arrived early for our ADR.
When folks book the Fantasmic Package, the CMs won't give you an ADR any closer than 2 hours before the show start time. So you need a minimum of at least 2 hours before the show for your ADR.
Most who want a good seat for the show enter the stadium about an hour before. When we didn't make the show after Sci-Fi, we went the next night (a Saturday no less) and entered an hour before (this was the end of Sept) and we got an amazing seat right in the middle, half way back. Unfortunately, for us it just wasn't meant to be that we'd see Fantasmic that trip! It started to pour and they canceled it.

What can you do?
Anyway, if I were you, I'd really try hard to get a 4:30p or 5:00p ADR at the very latest ADR and I'd definitely check in early in hopes that you are seated on time.
Good luck.