I'm not sure about expressing colostrum, but in regards to cluster feeds at your busiest time... hmm..
THere is usually a 20-40min gap between feeds during cluster feeding times, so I guess you just have to manage your time between those breaks.
Also, perhaps a sling that you can bf in might help you out.
I don't think you need to worry too much, you can find a way to manage!
Best of luck!!