Hey Jazzyvee,
Are they actually insisting or could you just ask for a wedge?
I'm a fan of IEMs in large venues for a few reasons. One is, the less bass you have flying around on stage leaking into mics or even blasting out of your amp, the cleaner it will be in the PA. Put that BIG AMP to use if you know what I mean. Second, the ability to build your mix specifically how you want it (will be traveling with your own monitor person?) is a great thing. For example, I run a stereo mix with my bandmates panned roughly like they are onstage plus an extra bit of hi-hat in my left ear. This obviously remains constant no matter where I stand or which direction I'm facing... You can be standing near the LOUD guitar player and have him completely off in your mix (not that I do that!).
Also, monitor mix consistency from venue to venue is very helpful. If you get into a terribly boomy or reflective room it has much less effect on what you hear and get to play along with.
I've never tried a bass board but know some drummers who enjoy the throne-mounted "kicker". I don't think it's really sound you get through these things, just kind of the impact of the attack and maybe some vibration. It's meant to trick your brain into thinking it's really loud. Or ... you can just teach your brain that your IEM mix is a beautiful thing.
We hope you have a fun time on this tour and it's an overall great experience. Making people happy by playing music is a treat!
Jimmy J