Hopefully, you didn't pay a lot for the kittens. If you got them from an animal rescue league, you could ask them to help you, since they should be health-checked from a league.
If you purchased them from a private owner, you can consider these "rescue kittens", which you have saved. If you purchased them from a breeder, there should be a health certificate. From a pet store that actually sells cats and kittens, go back to the store.
But, I have rescued kittens and given them homes. I have charged small fees such as $25 to $35 each kitten to insure a good home. I tell the people they need vetting. Kittens often have eye infections and upper respiratory infections. You won't get the money back, if this was simply from a private person.
I WOULD NOT take the kittens to the shelter, because they may put them down - they won't tell you this. I would simply get them vetted and make them family members. In the scheme of things, your kittens should live about 15 to 20 years. If you divide these costs by that time, it shouldn't be too much unless you have a vet who overcharges.
Our vet charged $45 for the visit; $35 for the medication/antibiotic; $15 for eye drops. Go to a vet who charges reasonable fees.