I guess I needn't have been so worried, they are still absolutely lovely and we had a nice time. They have 2 boys aged three and six, both loved Skittle so it worked well for playtime!
The thing I noticed most though was that I haven't talked trauma for a really long time, I haven't seen anyone that asked "so what happened?" and "what can you remember?" in ages. So I talked, I gave a reasonably brief-but-detailed-in-places kind of account of Skittles arrival. And much as it made butterflies swirl in my stomach and my hands go shaky, I didn't have that awful extended reaction I used to have to musing over the past.
I didn't tell the story and then disappear into my own mind for days, withdrawing from everything including Skittles. I didn't struggle with heaps of guilt or think about self harming. I didn't get stuck in NICU memories. I just felt a bit fragile and vulnerable for the duration of the convo and then gave Skittle an extra long squeeze and gazed a little longer into his deep blue eyes, remembering all I'd just said.