I was curious enough prior to the Prereleases to look into the four. Almost posted it here, too, but didn't know how interested people would be, and didn't know off-hand if the trainers were random or fixed (though I'd imagine they're fixed). Anyway...
Keeping in mind you get TWO of these groups (one being the one corresponding to your promo, and one other one, which I'm not 100% sure is random, but could be):
Charizard group:
Charmander
Charmeleon
Shauna
Tierno
Growlithe
Arcanine
Vulpix x2
Ninetales x2
Gyarados group:
Magikarp
Great Ball
Professor Birch's Observations
Shauna
Poliwag x3
Poliwhirl x2
Poliwrath x2
Machamp group:
Machop
Machoke
Level Ball
Great Ball
Tierno
Shauna
Hitmonchan
Diglett x2
Dugtrio x2
Mewtwo group:
Mew
Great Ball
Professor Birch's Observations
Tierno
Nidoran Male x3
Nidorino x2
Nidoking x2
Got these from watching Youtube openings of pre-release packs. (Not something I typically do, or find interesting. I had them muted in case anyone was wondering, which you weren't.)
I got Gyarados (which was my promo) and the Machamp group.
Keeping in mind you get TWO of these groups (one being the one corresponding to your promo, and one other one, which I'm not 100% sure is random, but could be):
Charizard group:
Charmander
Charmeleon
Shauna
Tierno
Growlithe
Arcanine
Vulpix x2
Ninetales x2
Gyarados group:
Magikarp
Great Ball
Professor Birch's Observations
Shauna
Poliwag x3
Poliwhirl x2
Poliwrath x2
Machamp group:
Machop
Machoke
Level Ball
Great Ball
Tierno
Shauna
Hitmonchan
Diglett x2
Dugtrio x2
Mewtwo group:
Mew
Great Ball
Professor Birch's Observations
Tierno
Nidoran Male x3
Nidorino x2
Nidoking x2
Got these from watching Youtube openings of pre-release packs. (Not something I typically do, or find interesting. I had them muted in case anyone was wondering, which you weren't.)
I got Gyarados (which was my promo) and the Machamp group.
