Thanks again for the responses from everyone.
Yes, we called the Hemlock Animal Hospital where we adopted them, and mentioned they have fleas. We went there within an hour of noticing and had them apply Revolution.
We didn't let them roam the house much prior to that, and since, have done a major vacuum/clean in the limited places they were. Also, they never got close to the older cat yet, as he's a bit nervous of them so far.
Also, just to be safe, we let the "Action for Animals" organization know about the fleas (they provided them for Adoption) since we noticed there were a bunch more kitties in the same cage when we went back for the flea treatment.
We wanted them to make sure other new kitty owners were made aware of this issue.
Since I had not seen any more fleas (just found one dead one) we let the kitties roam the house at will now, so they can get the attention they deserve