Think dad will be rather fed up of tomatoes and pomegranate in a few more week the way we are planning to shovel them down him! :)
Tomatoes (as in tomato puree) can be added to so many dishes without compromising the taste of the dish. Just think of spag bol for instance. That's already tomato based. My husband doesn't "do" cooked tomatoes - he thinks they're vile. He knows spag bol has toms in but what he doesn't know is that I squeeze loads and loads of puree in. !!
It's a bit like fooling a child really. Coffee for instance. He isn't a massive coffee drinker and because of that refuses to consider de-caff.
OK, I didn't make a big issue of it but I didn't discard the empty jar. I just half filled it with de-caf and when I make coffee I just get out both jars!! Sneaky eh?
Likewise, turmeric. You can add this to any dish that is already flavoured with herbs and spices. I wouldn't recommend the turmeric drink (I have tried it and even I think it's horrible and I'll give most things a go).
Perhaps initially cut back rather than out altogether. If dad doesn't mind fish then swap one red meat dish for fish of some sort. If like mine the only unbattered fish he eats is the occasional bit of (undyed) smoked haddock, then buy fish that is lightly dusted rather than battered or crumbed.
We do have soya milk which started off as my change of diet due to a health issue and now John has it on his breakfast. He likes yoghurt and I've swapped to soya ones. There isn't a massive difference between the two.
Cut down rather than out, all pastry and cakes and try and increase fresh fruit intake, organic for preference.
I can understand you all trying to get him to change because it gives him a better chance, well, at least it won't harm him, but life has to have some pleasure and making a complete change to your dad's diet means he isn't likely to enjoy it or stick to it.
Remember - slowly, slowly catches monkey. Creep up all the changes on him !!
Best Wishes