...Is it just as simple as sending them monitor outs? Just making sure the whole band is in each mix?
Yep! It's pretty much the same routine as floor wedges. Just send them whatever channels and levels they ask for.
Any compression so their ears don't get blown out?
If they bring their own...Most proper IEM systems have limiters built into the transmitter/receiver to protect the user. Shame on them if they don't. If it's any consolation, IEM's are less prone to feedback than floor wedges. If the whole band uses them, you are golden.
What about an ambient mic/mics, are they necessary, if so placement?...
Again, it's up to them to bring that. Many IEM systems have an input for a lapel mic.
With a good inclusive IEM mix, the band should hear each other very well. They may have trouble hearing audience members or anyone who speaks to them without being near a stage mic. To them, it's like having in ear plugs, but they can survive without it for one set.
If you have a free mixer channel, you may want to use a talk-back mic to communicate with them. Just plug in any cheap mic and send it to their aux mixes, but not to the main L/R mix.
Good luck.
