Commitment ceremony for dying grandmother

Hi everyone!


My wedding was originally planned for this October. Unfortunately, I was just diagnosed with a rare type of tumor that will require surgery and an extensive treatment. For the next 8 months, I will be immunicompromised, with little to no immune system function. I will also lose hair and feel sick most days. For these reasons, we decided to postpone our wedding until 2021 when we hope things will slow down and we can enjoy our celebration.
We were at peace with our decision, and our wedding party was appreciative for the delay, as most of them have no income right now. However, my future in laws called me to say I should “suck it up” and just do the wedding anyway because my FH’s grandmother has lung cancer. I am in no financial situation to get married this year since I am currently not working, nor do I physically feel up to it.
Despite the rudeness of the in laws, we would like to try to do a ceremony before God with the grandma. She is a lovely person. It was suggested by my pastor to do a small “commitment ceremony” over Thanksgiving when the family will be together. We would be committing to each other before God and our families, but not legally binding. There is no marriage certificate. It’s essentially a promise to God and each other, but it would mean a lot to the family.
Has anyone done this before or have any advice for how to make this work? We would want to keep it very simple and intimate at a family member’s home. Budget would be tiny. This sort of thing is new to me so any advice would be appreciated. Thank you in advance 💕