Okay...so you want just girlies? Or you want males and females?
What kind of Pleco, too?
You'll need to have more then a couple Swordtails, too. Preferably like 3 females per male...and they may be a little big for a 25 high though.
Female Bettas need bigger groups...preferably 4+ to avoid fighting problems. Or just one. And these don't really go well with Guppies...
So you really need to decide what exactly you want, then we can help with numbers.
Edit: Yes, Swordies, and Bettas will eat fry too. If they all were in a tank with Guppies...which I wouldn't recommend.
Protecting fry...Have lots of plants. Floating Plants, plants with lots of little leaves close together, have little hiding places, wood with little holes, little caves, rocks...things like that.