bear9298,
Your datums are your fixturing points. You can pick up your curved face using datum targets. Otherwise, it does not make a good datum. A curved face defined by datum targets does not provide a reference for perpendicularity.
My second paragraph was about priorities. What is more important, the holes or the curves? Your datums, your tolerances and your dimensioning should be based on your requirements, how you part will work, and on how you will inspect it.
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JHG