With the exception of rosey apple aphid fruit growers don't usually worry much about aphids except in immature trees. For these I'm not sure if oil helps much early anyway as aphids become established after pedal fall and I believe they are pretty mobile.

If you forgo the captan you can always use the refined oil commonly used today at petal fall or later as long as temps don't go into the '90s -just throw it in the tank mix. This is when calcium is first applied as well, although I never use it. Only my Honeycrisp seem to pay the price for this negligence.

the majority of my trees are 2nd and 3rd leaf. I think since I missed the oil this year I will apply the captan.

I have 15 Honeycrisp though I don't plan on letting them fruit this year. I wonder if there are any negative aspects of applying calcium since I will certainly be using the same mix on all my trees. I will see what google comes up with.

The reason I suggested not using Captan is because it is not compatible with oil. The only reason to spray trees with calcium is to get more of it in the fruit- mostly for better storing capability except finicky varieties like Honeycrisp that need a lot of calcium to avoid rot at some sites. .