Egglady,
Your lambs to the abattoir tomorrow will be absolutley fine, you can always move to slaughter - As confirmation Shetland Paul has given you the link that says so.
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 then clock, so you have 6 or 20 days from Wednesday as your first date when you can move anything off live.
Come back if the above is not clear, but don't panic you are fine with your proposals.