Sounds fine Danni. There are only so many races of 26 miles or more that you can do as a hard effort. I don't think that you are short changing these other races as you should still have a good experience at them. I didn't race London last year or Boston this year as hard as I could because of Comrades and I had a great time at both, enjoying the crowds and the sights.
I'm not sure when those races are Danni but I found that an autumn marathon did not compromise my Comrades training but a fast spring marathon PB put me behind a little. I recall that one of the training plans advised not racing a marathon any later than early February. Mine was a little later than that. There are others who have run fast marathons later than that and performed well at Comrades but I think it was not the best for me. I do marathons as part of Comrades training but normally at a comfortable pace only.
Thanks for the tip about the Hilton Danirr. It was too good to pass up so I will be deserting the City Lodge this year. I would still recommend that as a good option that is a lot cheaper than the Hilton, secure and very well located.
The start was easily walkable from City Lodge/Hilton/other nearby hotels last year.