I don't think you will get much breeding done in a 2.5 gal
tank.. but you might.. who knows...
I usually put my fry in a breeding net until they are about 2 weeks old, after that they are usually fast enough to outrun the bigger fish and there is a sponge cover on my filter intake. I think that I read somewhere that guppies are finished growing until around 6 months, but I'm not fur sure... I'd turn the heater up in your fry tank as well to around 80... That will make them grow faster as well as feeding them multiple times a day =)