It's a difficult decision. Any possibility that you could go and DH join you for some of the stay? Will your GC here miss you? How easily can you upticks and leave your home? It's not w matter of just shutting the door and hoping all will be well.
I don't think you should feel guilty if you don't go. The longest I stayed with my DD in Oz was 7 weeks, lengthened from 4 weeks when the new baby got a Strep B infection and spent time in hospital. My DGC here was 5 months old and I felt that any longer and we would have lost our bond, not good when I was about to become his daytime carer at 8 months.
I have visited regularly but health problems make the thought of the long journey scary and I am torn in two by the fact that DD in Oz is unwell and I could help in so many ways if I was with her and her three children, but then I couldn't look after 2 year old grandson here who I have looked after for 16 months. When I feel guilty I just remind myself that she chose, even if it didn't feel like a choice at the time<3 to live 12000 miles away!
Last weekend, in Rutland, the first statue in Britain of the late Elizabeth II was unveiled.