I'm currently practicing sentences that begin with
"I hope that..."
"It is likely that..."
"She said that..."
and I'd like to know if this sentence is correct.

"Is é níos dóichí go bhféachfaidh mé mo dhaidí inniu ná ní."

The only part I'm unsure about is where it says "...than not". I'm not sure if that is how an Éireannach would say it.

Go raibh maith agaibh!

D'fhéadfá an briathar a athrá mar sin, ach bheadh blas fadfhoclach amscaí air - I guess you could repeat the verb like that, but it sounds long and a bit awkward:
"Is dóichí go bhfeicfidh mé mo dhaidí inniu ná nach bhfeicfidh."
It is more likely that I will see my daddy today than that I will not.

Seo duit cúpla leagan is dúchasaí - a couple more natural versions:
"Is é is dóichí go bhfeicfidh mé mo dhaidí inniu."
What is most likely is that I will see my daddy today.

"Is dóichí ná a mhalairt gó bhfeicfidh mé mo dhaidí inniu."
It is more likely than not that I will see my daddy today.

Go raibh maith agat, a Abigail.
I like the last one best, but what is the word "mhalairt"? I've never seen it before.

"Malairt" means alternative, other or opposite. You often see it as "a mhalairt" ("his/its opposite.")

"scéal eile"
another story / an additional story

"a mhalairt de scéal"
another story / a different story