Yes, it is perfectly normal to feel a little bit (or ALOT) of sadness when something goes to butcher. If you didn't care for it, and care about it, then that would be different. I have had many animals done over the years and I still have to give myself a stern talking to on occasion when some of them go. I have also sent a cull cow to the market, that I KNOW HAS TO GO, with my son or someone else because they meant alot to me, and I just did not want to see them get off the trailer at the stockyard.
The butcher will be able to look at their mouth and tell that she is older, but best if you tell them. And it has to do with the calcification of the spine too I think. This also gives you a chance to think of the different cuts. Personally, I always get NY Strip and filet rather than T bones so the only big difference for me is the backbone. I like it because it is meaty, and is great to do like you would BBQ ribs..... or makes a great "soup bone". There are other "soup bones" so you will not be deprived.
I don't blame you for making this decision at this point. I had a 4 yr old 1/2 guernsey/ 1/2 jersey heifer butchered because I could not get her bred. She was a little older than I liked and some of the meat was a little tough. Not shoe leather.... but not quite as good as the ones I do @ 27 months. And because I had had such hopes for her as a nurse cow, it was tough.
Oh, also, I looked it up and it is 30 months. still won't help your older animal, but if you have a definite birthdate on the younger one, then get it done before 30 months and you can get the backbone if you want it. You will have to sign something saying it's birthdate or something. Some places are difficult to deal with, some pretty easy. Be honest, it is for your protection. You are not losing that much and only have to change the type of steaks.
'll be tough, but you can eat the meat knowing that they had a good life and you know what went into the meat.