Depending on your operating style, you’re going to want to get some separation between those antennas so radios/antennas don’t interfere with each other. Is it necessary to have all mounted in one location? If you can get at least a wavelength of vertical separation between antennas or greater for horizontal separation, you’ll do best. Otherwise, if you transmit on the 440 band, you’ll probably come in on your GMRS radio and your CB radio might even interfere with your 2-meter communications, or perhaps 10 meters, for sure. You just never know given the environment. Separation helps.
As far as using antennas for double or triple duty, it may be possible, but SWR is going to be an issue. It would be highly recommended for you to purchase an SWR meter so you know whether your antennas are able to accommodate a broad band of frequencies, plus whether you’re getting a lot of power back down the cable to the radio, potentially damaging it because of high SWR.
I run a number of repeaters on VHF and UHF and have had difficulty using general coverage antennas on like bands, such as 440 and GMRS. An antenna that works well on GMRS might have crappy SWR on 440. I have found that antennas tuned for your frequency work best, but then again, it’s more mission critical with a repeater and the RF coming back down the pipe to the repeater.
There are some antennas designed to cover 440 and GMRS, but I haven’t tried them. Likewise, 2M, 440 and possibly GMRS. But you most likely will find dual-band 2M/440 antennas. I’d check the specs while shopping and then ask questions about the antennas in forums such as ours here.
At one time, I had Comet dual-band antennas on all my repeaters and remote bases at my site, but eventually went to the Ed Fong antenna for my GMRS repeater because I needed something highly tuned to the GMRS frequency that the dual-band amateur antennas were not offering me, and causing SWR readings too high. I still have trouble getting great SWR readings for the dual-band antennas on the 440 repeater, a commercial VHF repeater and a 2M/440 remote base, and probably will swap them all out with single band antennas at some point. I even went to half-inch heliax cable for the GMRS repeater, but still have some occasional issues with the 440 remote base getting into the 440 repeater. And with my TV antenna mounted about 10-feet away, the VHF repeater knocks out some OTA channels, as well as FM broadcast reception when it is transmitting.
The thing about antennas is there is a lot of experimentation. My guess at this point is that you can use a dual-band 2M/440 antenna for amateur, another antenna for GMRS to get past SWR issues and the need to swap out coax all the time, and if you shop around, you just might find an antenna that will give you coverage on both 10M and 11M so you can get by with just one for that. I would try and get vertical separation between the 2M/440 antenna and the GMRS antenna (at least a wavelength or greater – a minimum of 10 feet, perhaps 15 feet) and some horizontal separation for 10M/11M by perhaps mounting on the other side of the house. The cable length on HF isn’t as critical as it is on VHF/UHF. But don’t skimp either on the long coax run.
I hope this helps a little.