Shout out to WI! "Cold enough for ya?" (just kidding, couldn't resist!!!) My ears will perk up for random Ryans now!
Kid vit advice, what a sticky wicket. Agreed that the multi-vits are mostly a scam and dare say potentially toxic....
I remember Laura talking about putting a liquid form on feet, Mag(?), it's highly ingestable that way. Have been meaning to look that up for my own family - and my bad, don't have the time to search-engine that one at the moment either.
I have a toddler (so not directly relevent for you, but may help others). He was good at swallowing and textures (as in no issues with eating or choking). I heard of a neat trick to get them to take their EFA pills, call em "gum" so it's a treat of sorts and let them chew on the pills (soft gels, due to being oils) and they will pop in their mouths eventually. My kid LOVES this, to me as an adult it seems utterly repulsive.
I give him D3s, Evening Primrose, plus a kiddie cod live oil which is orange flavored soft gel to chew on. He also gets those "Emergen-C's" pitched as "vitamin juice" - which is a big hit, because the kid never gets juice, only water, tea & kiefer.
Oh yeah, he also gets probiotics, right now he gets the occasional tube of "ThreeLac" (it's powdered and sweet - it has candida eating biotics in it too). I used to crack open pills and put them in his food, but now the thinks it's too grainy. Or I put whey in his "special 1/2 & 1/2" [I forgot, he does get a weekly shot of dairy, but this is a good cause - it's a bone/veg broth cube (frozen in ice cube tray), molassis or honey, fresh whey, & non-pasturized cream (if I can get it, huge hassle, we've been subjected to one of the huge crack-downs)]. But my point is, probiotics assimulate vits in the gut and there is a huge amount of minerals & vits from homemade organic bone w/veg broths, plus the bone gelitin sooths/heals the intestines (if leaky gut is an issue. Incidentally, kiefer actually rebuilds mats/colonies of pro-biotics in intestines).
There are also plenty of liquid versions of vits with/and/or herb tinctures - but that falls into the groody-must-be-disguised category others have spoken of. But a smoothy with lightly steamed kale and with whatever you fancy these days (plus a glob of coconut oil to assimulate the fat soluble vits) will go a long way for vits that co-factor/enzymes, plus will stop grey hair on us.
My heart goes out to you with having to share your children in a situation that potentially compromises their health. That's tough. On our end, far less significant than what you have to face, is that we send our son to a hippy/nature daycare and they're just over the top with the tofu and pasta - they haven't questioned conventional dietary "wisdom," ehem, brain washing. But it's something that used to tear me apart. When all is said and done, I've chosen to take it up a notch at home to compensate. I'm also not asking them to alter his individual menu, primarily because he IS thriving physically and because I don't want him to associate food with emotional/social isolation. Additionally, it's all organic (even if it is out of a box, for what it's worth) so it's better than he would get anywhere else, including all of our relative's and most of our friend's homes if they are babysitting or holidays. I also feel (or is it rationalize??) that since he is getting exposure to conventional foods - nutritious food won't be something he rebells against as a teen (man, have I heard stories of kids turning into closet junk food rebels!).
We also talk about how nutrition impacts not only his physical health, but his mental health too, that they are directly related. We've also had some opportunities to talk about how fast food has made us both physically ill at times.... in typical toddler form, he asks, "WHY?" like why the hell did we just get those drive thru cheese fries if you're supposed to care for me and we both just got horrid gas pain? And I've had to talk about (as in eat crow) about how you (as in doofus mom) just have to learn the hard way sometimes, and trust your body. But he also got a direct example of how something might taste "good" but may harm you, which I spelled out for him. Why I started on this tangent was that you can at least influence your daughters' relationship with food, and in turn, they may be able to influence your EX's household in a non-threatening manner (my going assumption is that you would be told to stuff it if you broached the subject directly with her).