Firstly, the warning/5 for delay/5 for delay/15 UNS process if for team personnel simply being in the restricted area (or on the field) while the ball is in play or in the continuing action after the ball has become dead. This would be without contacting or disturbing an official in any way. (Obviously, this does not include "players," as defined by rule.) First instance: Sideline Warning - S15 only. Second and Third instances: Delay - S21 plus Sideline Interference - S29. Fourth (or more) instance: UNS - S27 plus Sideline Interference - S29.
Secondly, if an official has physical contact with, or has to do something to avoid contact with, team personnel in the restricted area (or on the field), this is a 15-yard UNS foul - no warnings or "minor" penalties before the "big one." (Again, obviously, this does not include "players," as defined by rule.) UNS - S27. The penalty statement does not include Sideline Interference - S29, but no one will fire you if you use it, too. It will help everyone know what happened. They may not like it, but they'll know.
In the instance described, the two flags should be combined into a single UNS penalty. They'll get the message. Of course, that will be after the obligatory, "We were behind the play!" Or, "That's just a warning!"
Nope. Flag it for what it is - UNS.