Their kits - alas - as a wee bit cheaper than "yours".Even with "multi-buy" from you, with the postage and all.Please don't be upset.
From personal experience I suggest you avoid DS1307 unless time accuracy is not important. I have one and it looses about 7.5 seconds per day. ... I also have several DS3231 and they are a lot more accurate at less than drift 2 seconds per month. The DS323x range are more expensive than DS130x but in my mind worth the extra cost.
I haven't done it yet, but I am looking at handling the drift in software. Add or subtract a second every few hours