The term "itinerant" is thrown around a lot and often inaccurately.
Itinerant means you operate at varying locations for unspecified periods of time. There are several frequencies set up in the business pool for intinerant operation and they still require licensing. They don't require coordination but they do require licensing.
There are only a handful of those channels. The business band radios they sell at costco, bj's and etc, operate on business frequencies that are not itinerant and do require licensing and coordination.
One could also operate on GMRS and MURS and FRS in an itinerant fashion. Similarly, those are shared, uncoordinated channels and you are likely to encounter many other users there that could adversely effect how well you can communicate.
The FCC has a pool of frequencies in the Part 90 section called Itinerant channels. These channels are perfect for a tactical repeater setup.
A big advantage to Itinerate channels: there is no need to go through frequency coordination or incur coordination fees. To receive a license, all you pay are the FCC regulatory fees of $260.00 for 10 years. Yep, 26 bucks a year, or $2.16/mo. You are licensed for low power (6 watt) anywhere in the USA. Plus encryption is legal.
To receive a license you fill out a FCC form 600, pay your $260 bucks and you are good to go!
The intinerant freqs, and there are about 3 on UHF and 5 on VHF, each have restrictions and limitations as outlined in Part 90. So look through them and see which ones you can use. At only 2 watts, the only restriction that comes to mind are geographic restrictions that a couple of the frequencies have. Then listen to those frequencies and make sure they are clear and do not have interference. Keep in mind, they could have interference at any time without warning. On one particular channel in my area that is itinerant, the main user is a fleet of cement trucks that use the channel for their car-to-car communications even though that channel was probably set up for job site communications only and it's hard to share that channel with them using their high powered mobiles on it despite using coded squelch. And now that very same frequency has a licensed and coordinated user on a splinter frequency about 2.5 khz away from it (an EMS) that is audible over that frequency just as if it was on the frequency.
It seems like many people are confusing the business radios like they sell at costco that come with about 30 different preset frequencies. Those are not necessarily itinerant frequencies and in fact, most, if not all of them are not itinerant. You can't just go buy those at costco, mail in an application and start using them when you get your license. It's not GMRS.
You still have to get coordinated for the frequencies that those use.
You can request the frequencies that are in there but you have to get with a coordinator that will agree to that and pay their fee (in addition to the license fee). If you don't want to do that, you'll be limited to the few itinerant channels or perhaps MURS, which, MURS is actually more quiet and usable in my area than the itins. You might also look at some of the business grade FRS radios that are out there. I believe retevis makes one that will hold up to the rigors of every day use. Of course, you'll be sharing your frequency with singing 5-year-olds but that's keeping it legal for less.
Business Radio Licensing
If you are using a two way radio for your business, licensing a frequency with the FCC ensures that you are using a frequency that is reserved specifically for your business. This prevents interference that commonly occurs on the frequencies that many radios use as defaults. This interference is a nuisance that is distracting and reduces productivity. A business radio license (FCC Part 90) is good for 10 years. After 10 years you have the option to renew, or let the license expire (and stop using the frequencies).