I wouldn't put the pair in the rearing tank with such young fry. They may not eat them, but as LL said... if it moves, it's dinnertime!
Males can harass a female to death so don't put more than one male with a female. It's usually better to have a 3:1 ratio of 3 females to every male. But if you don't leave them together too long, one on one should work fine. Just keep an eye on things, and if the female is clearly having problems from the male's advances, move the male.
Basically, guppy/endler "breeding" goes like this: Get female. Get male. Put them together for 2 seconds. Breeding completed!
Point being is that guppies and endlers breed like crazy. The males will do everything they can go breed with the female. And even with the female trying to get away from the male, the males will sneak up and try to breed with the females.
I'd leave them together for a day or two. Then put them in their own tanks again. Watch the female. She should grow increasingly larger until she drops her fry in a month.
If, by some odd chance, the female did not get pregnant, then give it another try. But, honestly, these fish aren't called "millions fish" without reason.