My father was alcoholic, but the older he became, the less he drank.
The last times he drank beer, it was just 3 bottle of low alcohol % beer, so he liked it, but didn't get drunk anymore.
He even told me "I can't drunk as much anymore, i keep it at 3 bottles.", and i know what he drank before he his kids XD
So they could just have 1 a day, as you can only give 1 a day... without mods.
Many ex-alcoholics are still taking one or a few, as they still like it, but don't get addicted anymore.
I give Pam Parsnips gold quality, and buy Shane beer, and in Summer i grow him some peppers.
So Pam gets none, while Shane only gets them in Spring.
I guess we gotta work with what we have, and i see Stardrop Saloon always sells Pizza, so you can start buying Shane those.
You can Roleplay by getting Shane Pizza, so you won't encourage him to drink more Beer.
I think it would be better if Shane's Love for Beer would go, and it becomes a Like after the rain event with him. Just for the taste, not the habit.
Pam may be able to handle 2 more Beer a week, as she's older and probably stronger physically... kinda used to it by now, i think.
I guess using mods on PC would be best, as you'd just remove the Love gift for your own feelings.
I think this game is to make you feel better, so adding on to that, would increase that effect.
If someone can and will make such mod, ask them to make Beer a hate gift, as Pam and Shane could not even like the taste, and only use it to drink away their problems.
Hope i helped a bit by giving my opinion on it, hope you'll find a nice way to deal with it. :)