Mary,
Your doctors are correct, I believe, about the non invasive tests for heart problems. Some are better than others, for instance, an EKG tells VERY little unless the heart is acting up at that specific time.
An Echocardiogram is better. That's how they found that my husband's heart is not pumping enough blood. That prompted the heart cath which found 4 major blockages in areas that they could not easily access without him going on the heart/lung machine.
Where the blockages are located determines whether the by-pass(es) can be done without going on the heart/lung machine.
Prior to that, Bill had already had angioplasty twice (for two different arteries - heart attacks) about a year or two apart. They weren't using stints at that time. He did fine with the angioplasty. Those arteries did not plug up again. The 4 new ones they found weren't in places where stints were the best choice.
My point is, a lot depends on exactly where the blockage is located. Apparently, your's father's heart attack was a fairly mild one but there will still be some heart muscle damage.
A lot depends whether he is in very good physical shape. My husband was and he managed VERY well for a long time and his doctor is astounded that he is able to do the things he does today. A lot of people whose heart isn't pumping any better than his would be waiting for a heart transplant.
I think that your Father will probably do well (unless he has other complications). That's just a lay person's opinion.
I am so sorry this has happened, expecially at this time (when you have planned to go away). He will probably be fine but I sure understand your reluctance to go.
Please keep us posted about how he (and you) are doing.

Shirley