I do not think your pronoun or your tense conjugation of the work estar are correct. Future tense should apply, even though it is "in a moment". .
Are the "ellos" (them) the "chicos" you are talking to or señora Perales?
Ellos would not be the appropriate word in either case.
Now, this would depend upon the country as to whether you would say (more in Spain) = con vosotros OR everywhere else = con ustedes.
I always used "ustedes" (more formal) with my students because they felt "most grown up!"
Just happened to think you might like to know the translation. Sometimes, if you aren't absolutel sure what to say, try the following:
1. look at the Spanish carefully
2. translate into English
3. answer FIRST in English
4. now try the Spanish and
5. verify with the base sentence
Boys (lads), I'm going to speak with Mrs. Perales. (that is one independent sentence and to avoid a run-on sentence, either end with a period here OR a semi-colon OR add the word "AND."
In a moment I am with THEM.
Believing you intend to say, "I'll be with YOU(-you-all) in a moment, here's my answer.
Chicos, voy a hablar con la Señora (Sra) Perales and I'll be with you in a moment.
You don't need the future really, if it is in the "immediate future."