Dave, because you are going to ship a lot of items in the next month/year and because I am shipping a lot of packages every day using postal service and couriers service this is what I recommend;
1) Get an account with a local courier service, like TNT, DHL, Fedex, etc, the one that has good pricing/service, but the also look at pickup service and drop off locations in the area. They key is your time, not the cost.
They should provide you with shipping software and a free label printer, and all the packaging material you might need.
Yes you would pay a monthly fee, but your time is more precious.
If you don't want a courier account buy a used label printer, like the 'ZEBRA LP 2844' or 'Zebra ZP 450' and the thermal printer paper.
2) Buy a scale that connect to the software, like the 'Mettler Toledo Model PS60' (you might have to get a parallel card)
3) Get any service for online/software postal shipping like the 'Click and Send'. I use Endicia in the US, which is great. It offer commercial rates and I just printout the label, take it to the postal office and drop it off (if I miss the daily pickup). If the postal service doesn't pickup from the office, consider maybe the pick it up from the house?
Not having to stand in line at the post office, is the best thing ever, you would agree. That is such a time waster.
Hope some of these suggestion help. Wishing you and your family a Happy Christmas and a happy New Year.
Rutger