Generally speaking, breasts will be on the smallish side...but (if it were me) I'd be willing to gamble I'd get larger-than-average "MTF" breasts, given your family's "ridiculously large breasts".
Age is a factor, but it's not the be-all end-all of whether or not you get breasts. In addition to estrogen, one can take herbal fixes for breast growth (hint: Saw Palmetto has on a warning label "women should not take this, because it may result in unwanted breast growth". Figure out the dose, slowly increase it until you start feeling breast buds (I did), and then continue until you get on HRT.
Red Clover extract was another herb that I used prior to HRT. It comes with a dropper...half a dropper + 2-3 squirts of a skin softening lotion, rub on breasts for as long as your arms hold out (or about a minute...whenever you get bored). Rubbing pattern is: starting at 12 o'clock, rub inward and down to 6 o'clock, and continue to the outside area, and back to 12. Left breast is one direction, right is the other. (This has something to do with the duct work inside, it aids in growth.)
Also, you could take menopause supplements, over the counter stuff. (I got "maximum strength").
All these things did not affect my libido or man-parts in the least, but I did have noticeable "breastlings" soon after starting. Nips were about 1+" over the sternum area. Not much, but then again not bad considering these were just herbs.
There are some safety/overdose concerns iirc, so please google things and find out for yourself. I did the herbs not for any hope of getting boobs, but more because I read here that the phyto-estrogens of supplements will sort of "prime" the receptors for the actual E, should you get on that later on...since they are primed, one *may* see more rapid than normal growth.
I know I have. Not as fast as my friend, but then she's younger than me by about 20 years. (I'm 48, with almost-B cups after 9 months)
Even if you get on E, yes libido etc will go down (
almost certainly), but once you get breasts, and you go off E, they will stay there, only slightly and very gradually reducing in size, but you will get your male sex drive (i.e., erections) again.
Hope this helps, good luck on your journey and wherever it leads you.