You are doing a good job, dont underestimate yourself. If chicken's feet touch the ground, they're going to get worms, I dont care what anyone says.
It's always best to keep everything as dry as possible. Warm moist/wet soil is worm soup.
I use sand in my pens and coops, even nest boxes.
Sand...
Valbazen will treat dogs with worms requiring a longer treatment period if I'm not mistaken.
You can purchase a 6 month supply of Interceptor Plus from your vet with correct dosing weight for about the same price as a 500ml bottle of Valbazen and only give one chewable tablet to your daughter's...
Do what the vet advised you to do since you've never wormed your birds. Capillary worms are killers, you dont want to mess around with them. Valbazen will take care of them.
Dose the large fowl 1/2 ml at a time though. If you give them 1ml all at once orally, they can aspirate. Have two...