u/s in 2 hrs and then IUI? it doesn't make sense? what makes them think that u will release in 2 hrs?? I've never heard of such precise predictions??. Frankly I don't know if any clinic would be willing to do this.
Anyhow in my opinion you should talk to Dr. Check about this. Tell him about the clinic being very accommodating and that u/s in 2 hrs time is kind of expecting way too much from a small local clinic.
It seems like he is a very understanding doc so I feel he will understand this...