Adding live plants to the tank during the cycle is not dangerous at all; in fact, it is beneficial. I don't know if only few plants will help speed up the cycle, but a tank full of plants cycles much faster than one without them. This is because plants consume ammonia and nitrite, as well as nitrate to a lesser extent - all of which are present during the cycle. Ammonia and nitrates are plants' nutrients.
I'll put 2 or 4 of my current angels in there (another 2 will stay in my 30 gallon tank); then I'll get 3 rams, and some cherry barbs, harlequin rasboras, zebra danios, and diamond tetras or emperor tetras. I love all of these fish. I'd also like some rainbows but because they're not so small and need to be in schools, I'll get rainbows next time I'm getting a bigger tank (I'm hoping at least 125 gallons) .