Edit: Nevermind, I found out a way to tween it. I placed a Part into another Part, and when I tweened the another part, the placed part moved with it. Anyway, thanks for trying to help!
When tweening the model, if the CFrame of the PrimaryPart is tweened, all parts welded to the PrimaryPart will move together; if the Position of the PrimaryPart is tweened, only the PrimaryPart will move.