It's a good deal and will determine if some of the feedlots will bid on your calves or not. The first calf born is the key. The rest of the calves within the season will be aged as old as that first calf. Just keep your calving records as you normally do in your daybook or wherever you would normally write such a thing. Call the Angus Association to check out their program, Angus bulls or not. It's fairly cheap and several tag options. You can tag with the official source/age tags at preconditioning time or other working occassion for the programs that require a unique I.D. besides your ranch tag. IMI Global doesn't require a different tag besides your ranch tag, provided you tag your calves already. It's a bit pricier but also a solid program. There are others such as AgInfoLink, Cattlelog, Samson, etc.
Buyers will factor that age/source money into their breakeven when they purchase calves. When selling fats it's worth from $15 to $35 per head to the seller, more in those really off times of the year. Just my outlook and experience, no absolutes here.
HP