You can't really cycle anything without having some sort of ammonia in it. So if you put the frogs in now then they would be a source of food for the bacteria that are needed for aquariums. The bacteria eat ammonia and help keep the tank clean and are a vital part of every aquarium.
Really a bottle of instant cycle of what ever its called would be a good idea also, but I think it is rather expensive.
I would put the frogs in when you are ready to, as long as the water is around 7 PH. And then just check the PH once a day or so until it stays around 7 without you having to do anything. Then PH checking wouldn't become a everyday thing.
In a tank that small just putting them in and doing like above should be good enough for it to cycle. And if you are monitoring the PH and water it should be fine.
I am going by what I do for fish, don't know exactly about aquatic frogs. But I am guessing they should be about the same.
Don't take everything pet stores tell you as true right away
I have been lied to many times by big chain stores. But usually small family or local owned stores are better.
You do have chlorine remover right? If you don't have chlorine remover and didn't use it in the tank you just set up I would wait a day or two, maybe a bit longer. Chlorine would burn their lungs and kill them.