Egglady,
Your lambs to the abattoir tomorrow will be absolutley fine, you can always move to slaughter - As confirmation moleskins has given you the link that says so. However MS is not quite correct on your standstill on the sheep.
You can also ALWAYS add stock to your holding, it simply restarts the clock on you moving anything OFF, except to slaughter.
So your piglets arriving today trigger a 6 day standstill on moving any sheep off (except to slaughter) and a 20 day on moving any pigs off (except to Slaughter). So you will have a sheep standstill til Saturday and a pig standstill til 20th November - standstill ends at the clock time they start, so if your pigs came onto your holding at say 2.12pm today, 6 day would end at 2.12pm on Saturday.
However on Wednesday when the ram arrives, he will restart the clock, so you have 6 further days before you can move sheep off.
You cannot move pigs off for 20 days after today (the day pigs came on). Moving the ram on wednesday only creates 6 days on the pigs, which is shorter than the existing 20 days so that original dates holds.
Come back if the above is not clear, but don't panic you are fine with your proposals.