Sneezy congested cats, help...

I have seven cats, all up to date on shots, one cat began sneezing a week ago, then he seemed to get better, but now he has leaky eyes and is a little congested, he has continued to have a healthy appetite and is playful, last night one of my other cats began sneezing, and she is very congested, she is also still eating and being playful. I have been crushing up lysine for them and putting it in there food and I am going to buy a dehumidifier today for them. I went through giving all seven of them antibiotics before when they had URI's. My question is do I need to get an antibiotic from the vet or will they will be fine with lysine, baby saline nose drops and a dehumdifier? I really don't want to go through the antibiotic course again

Steam in the bathroom is always good.  Also, a vaporizer (not a dehumidifier) will be best to help open up the nose.
 

Why don't you make a quick call to your vet to run it by them? It's so hard for someone to diagnose your cats over the Internet. Your vet has a better feel for them and their health.