So far both of them are a rumor. The official (and still some rumored) cast list is pretty impressive, but does not have either Fillion or Longoria listed, nor are their characters listed.
As to Ant-man and The Wasp. They are married to each other, and if they follow the Ultimate story line, as they seem to be doing (casting Samuel Jackson as Fury is straight out of the Ultimate Avengers) then having Ant-man and The Wasp in the movie could mean they are going down a dark side-story that could become a main story line.
As to their powers, this also depends on which version of the Avengers they use or borrow from. Also remember that they were created in the 60's, so yes, some of the powers would be groan worthy now.
In both versions Ant-man has the ability to shrink to the size of an ant (sometimes smaller) and can control ants to do work for him using a helmet he created (he is a genius on the level of Tony Stark). Pretty much in both versions this ability is from a particle discovered by him if I remember right. It was also discovered that this particle could make someone grow to giant size (Resulting in various versions of Giant-man/Goliath).
In the standard Marvel Universe The Wasp's ability to shrink down and grow wings came from her exposure to the same particles that gave Ant-man his abilities. The particles (Pym Particles btw) were modified before being given to Janet, thus resulting in the wings and the electric shocks she can shoot. Her shrinking increases her strength based on the ratio she shrinks. Later on she could also increase in size, and the abilities modified themselves thusly, minus the wings. (don't try to rationalize the standard Marvel Universe, your head will quite literally explode) Oh yea, she also has antenna she can sprout to control insects.
In the Ultimate Universe version, the abilities stem from her being a mutant, and are limited to her growing small (fractions of an inch if need be), bio-electrical shocks, and flight. It wasn't until much later that Pym gave her some of his particles allowing her to grow large (an ability she rarely used).
In both universes she has been killed off.
So, maybe knowing a bit about the characters back story before judging a book by it's cover would be prudent.