Is my dog gonna be OK??? Please help!?

I just got home from work, and my piggy dog (over 100lbs pit bull-5 years old) ate an entire bottle of doggie daily vitamins (Senior blend)100 tablets! I called the vet, they say he should be OK, but to keep an eye on him. But I'm so worried, should I take him anyway? Am I panicking for nothing? What should I watch for? Could he die? Please help! (yes that's his mug on my pic)