The only thing that I can say is take it slow.
Give the older cats lots of attention.
If the kittens get along together then I would  keep them in the same
room with the "usual stuff" and a couple of the older cats toys and
some new toys for the kittens then let the older cats curiosity
take over.

Yes, they will, but it's normal and should be over within a week or two.
My approach with all the cats so far has been straightforward with
possibilities for retreat for all parties and no force involved.
It has worked so far, but for the cats to become real friends it takes
several months.

Good luck!

Carola

It'll actually work better to have multiple kittens than it would for a
single kitten who wouldn't have any playmates and would harrass the older
ones just wanting to play.  BTW, get the girls spayed ASAP. Females can
become pregnant at 4-5 months, and you don't need that complication to add
to the others.

I just added two kittens to my home (5 mos.) in addition to my two adult
cats (6 & 7 years). I was lucky, I have a spare bedroom where the kittens
stayed for a few weeks (they had sniffles). The older cats knew they were
inside, certainly could smell them, and were very curious. The quarantine
also let the resident cats get used to the smell of the kittens. After the
sneezing stopped I let the wee ones out and it's been a blast! Now, that's
not to say that there weren't some tense moments - there were - but careful
planning can eliminate a lot of the problems that some people experience.

I truly believe that some of the more severe problems (inappropriate
elimination, etc.) can be avoided if you provide litter boxes for everyone
and have plenty of food down.  It's also a good idea to give extra special
attention to the older adults. I've always believed that it is better to
have multiple kittens than just one. The kittens will have each other to
play with (no one can play with a kitten the way another kitten can) and
give the adults some time to adjust.

Good luck.

Fran