I hope that's okay.

I'd say.

Nee, das hört sich nicht so gut an.
Ich muss hiermit einen Fehler unsererseits eingestehen und kann nicht einfach davon ausgehen, dass es ok ist.

(We apologise for the error) ? ...and hope it has not caused any great inconvenience.

z.B.

I hope it's not a problem.

Are you saying: I know we made a mistake but hope the delivery was nevertheless acceptable?

You're okay with "I hope it doesn't matter" but not with "I hope that's okay"?

How about "I hope you don't mind"? or "I hope we didn't screw up too terribly"?

Frankly, I'm not quite sure just what you're looking for. "ich hoffe, das ist nicht so schlimm" isn't exactly a paragon of style, either.

Vielen Dank euch allen.
Ich entscheide mich für #3.