Introducing 2 male kittens to 3 female senior cats

We recently adopted two male kittens, approximately 4 months old. We have three adult cats who are all females. They are 12, 14, and 16 - aka the "Golden Girls." We did not get the older cats at the same time and they did not grow up together.

With the kittens, we started by keeping them in separate parts of the house from the adult cats - the kittens had a bathroom and hallway in the basement, while the Golden Girls had the rest of the house. We gradually began letting the kittens explore the rest of the basement without the Golden Girls present. During this time we also fed the kittens and Golden Girls on either side of a closed door, working up to a baby gate with a blanket draped over it, to the baby gate without any obstruction. We've done scent swapping and room swapping as well.

While doing room swapping, we've put the kittens in their carrier in the area with the Golden Girls. The girls sniff and check out the carrier, but there is generally no hissing. However, when we crack a door so the Golden Girls can see the kittens walking around, they hiss and even growl. One of the kittens got out when the one of the older cats was out and about, and the older cat charged at the kitten while hissing. We picked up the older cat before she could do anything.

We recently started letting the kittens out in the general area of the house, with two baby gates stacked on top of each other to prevent the Golden Girls from attacking. The kittens are naturally curious, and approach the Golden Girls. Two of the three respond by hissing, meowing, and occasionally growling. The other one just runs away. This has been going on for two days now. When can we expect things to improve?

How do we integrate everyone as seamlessly as possible? Thank you.

anyone?

How long have you had the kittens?  

We brought them home November 9, so almost a month.

Also, in the last two days everyone has eaten breakfast together, unobstructed - this was by accident. Everyone was happily chowing down mere inches from one another. But when breakfast is over, the old behaviors return.

Tonight one of the girls, who we consider the alpha, poked her head in at the kittens behind their baby gate. She and one of the kittens bopped noses and sniffed one another. She meowed, but no hissing or growling! She did this twice.

The other two girls haven't improved much, though. Still growling and hissing, with one swatting at the kittens. They only hiss and growl when making eye contact with the kittens, or the kittens start approaching.