Congrats and good luck. Smart to start with some older experienced animals. Mineral should be offered free choice. Use a Hi-mag mineral in the spring due to fast lush growth of grass being low in magnesium.
We feed our hay free choice in big round bales. Don't know if that is what you have in mind. Our rule of thumb here in winter is 1 round bale per 20 head per day. Our bales are 5x5 and weigh in the neighborhood of 1000 to 1200 lbs. This is just an average general basic to work off of. If you feed small square bales you are going to have to figure at least 1 per cow per day at a minimum. If there is some grass/green growth, they will eat a little less hay.
As for feed. If they are used to getting feed, then try to find out what they were getting fed before. Easier to start with the same if possible. Beef cattle do not need alot of extra feed. Most of us feed a little to get them to come into a catch pen and to keep them calm and friendlier rather than them running wild with no human interaction. Maybe less than a third of a 5 gallon bucket a couple times a week? We feed about a 5 gallon bucket per 7-10 head twice a week or even only once a week. They learn what a bucket is for. If they are thin you might want to give it a little more often, but they are not dairy cows and do not need to be making tons of milk and they need to be able to go about being beef cows on basically hay and grass. They don't need to be too fat, but the one with the calf doesn't need to be losing weight either. The one that is short bred you don't want to get too fat as that can lead to calving difficulties.
Yeah the one with the calf a little thin and the owner told me he has them on a mixture of corn ..
Best of luck.