"Someone will go with you."
Translation:Jemand wird mit dir gehen.
In this sentence, IMO, irgendwer works as a synonym for jemand. At least in my regional (Northern) variant of German.
Thats strange, I thought the norther you go, the more people care to speak proper high german. Irgendwer (and irgendjemand) have a stronger conotation of uncertainty. Jemand is an unspecific person, irgendwer is a "really" unspecific person.
to me, irgendwer has a conotation of indifference like "I don't care who" while jemand tastes like "someone from around here". Irgendwer and irgendjemand seem more similar to me. (from South Germany)
"mit euch" is not good, only "mit dir", why? English you makes no distinction and the context gives nothing to decide.