That does sound tough. I do not like being the one to make all the decisions regarding my husband with dementia. So, you've taken on this role and I feel it's a tough one as you've stated due to family requests.
Perhaps build your case Re: why Dad should not travel. Line up the positives and negatives, share your findings with family and logically explain that Dad comes first, his needs take precedence over their desires, etc.
Good luck! 🫂