Need some advice!

I posted a while ago whether i should postpone my September wedding & you ladies were very helpful so im coming again for some piece of advice. I 100% have to postpone because my sister is in the hospital with covid, has been for a while but her condition worsened and we almost lost her twice, they say she will need many months close to a year in rehab and there’s absolutely no way im having this wedding without her. I reached out to my venue and they spoke to us about some dates, none that we wanted.. they arent letting us chose our date & we came to terms okay they arent gonna budge so we were almost in agreement to a 3rd in September which is Friday & labor day weekend.. heres the thing, we all know Fridays go for cheaper & a holiday weekend even more so.. they told us theirselves on our initial consultation but they are refusing to give us a discount, they are charging us for a Saturday evening which is double the price & when we asked can we have some stuff thrown in then they said “we arent going back and forth with you, we will throw in a French Fry station” i felt so angry because its like you are now choosing for us again.. we asked if we could have two stations he said no and we have to make our decision by Friday or we will have to stay with our septembee date.. i will note i havent been able to do anything planning as we are in nyc & i havent been in the right beadspace & also our contract says nothing about postponements only if we cancel all together. Anyways my question is should we take the loss & go with that friday at full price or have our friend who is an attorney send a letter & see if they will change their minds? Thanks in advance to those who read this & respond! 💗