Trapped stray kitties aren't strays

On one of the coldest nights of the year, I saw a fluffy white cat with spots near my house in the country. I posted on Craigslist, hoping to find an owner, but got no response. I saw this cat several more times. She seemed to live under a trailer with her kittens, according to the trailer owner, who didn't want them there. I started setting out a trap each night. But instead of a litter of kittens, I caught 1 kitten, the teenage mom cat, her 2 brothers, and a feral tom who took off shortly after his obligatory trip to the vet. He won't be making more kittens or making other cats sick, but the 3 teenagers (about 7-8 months) are obviously pets. Someone raised them and loved them and threw them out for the winter. I can't treat them like ferals. They obviously want to be pets again more than anything in the world, and they love living indoors. They are so cuddly: Cyril jumps in my lap when I sit down with them, and Sterling winds around my legs and begs for pets. That works fine, but I need a third hand when Mallory comes nuzzling around. I alternate hands between her and Sterling (until she swats him across the face, as she's won't to do.) The baby girl Lana is almost 3 months and has never been handled, but she's coming around. Her short little life must have been one long terror.

I've taken them to the vet for shots, neutering, and microchips. The girls will be spayed in a few weeks, when Lana is big enough. They are the sweetest cats, the best pets you can imagine, but there's no room for them in my house. I'm at crazy-cat-lady level with 5 cats of my own (3 ill) and a collection of foster cats.

I'm asking a rehoming fee, to partially cover their medical bills (and hopefully to deter evil doers), and I'm offering a discount if you take more than one. They've stuck together through so much! The black and white short-haired boys or the long-haired white and gray girl and her baby would be good pairs.

If you're in Texas or an adjacent state, I can get them to you. PM me and I'll direct you to the sponsoring rescue's application page.

Can you think of anything else I can do to get them out of my house into their own homes? I've contacted rescues (all full), posted a courtesy webpage on one of the rescue sites, taken them to Adoption Day, posted on Facebook and all my mailing lists, posted flyers, dragooned my friends into posting on their lists and bulletin boards, and posted on Craigslist with a link to a rescue site's application page.

I have an appointment on Wednesday with the Humane Society to talk about surrendering them, but that's breaking my heart. I've never surrendered an animal to be kept in a cage (or worse). Other rescue folks say that it's a good option, but I'm hating myself for it already.

Sterling
[url=https://flic.kr/p/mQA5kS][img][/img][/url]
Cyril
[url=https://flic.kr/p/mQyiwB][img][/img][/url]
Mallory
[url=https://flic.kr/p/mQA5mU][img][/img][/url]
Lana
[url=https://flic.kr/p/mQA5Bo][img][/img][/url]

UPDATE: I did take them to the Humane Society. The people there were very nice and already had a method to return them to me if they aren't adopted. Sterling's already found his home. I brought Lana back home because she was too feral, but she's getting more friendly every day. Thanks for all the support here!