Does anyone have any tips on helping a toddler cope with stranger anxiety? Especially when it comes to health checks?

We just got back from Kynan's 18m CHN check up and it was pretty much a disaster. I had to go to the post office first and when I put Kynan back in the car he threw a tantrum because he realised we weren't going to the park so that wasn't a good start. I was aiming to get to the health centre bit early but DH had left the carseat straps all twisted so by the time I sorted that out we didn't have a lot of spare time. Within about a minute of getting there the CHN was ready to see us. To make matters worse our usual CHN, who is aware of how sensitive Kynan is and takes her time with him, is on leave until next year so Kynan had never met this CHN before. He had his back to her when she came out of the room and got startled when she said hello and he started crying. She wanted to shine a light into his eyes and he really freaked out at that and screamed & buried his face into me. There was no way he was going to let her get close enough to do the usual checks! He was really getting quite hysterical. The CHN ended up making us another appt for a few weeks time in the hopes that he'll be having a better day but I don't think it'll make that much of a difference.

I ended up feeling a tad defensive as I got the impression that she felt like it was all a bit excessive (although maybe it is?? I've never seen another baby/toddler react as strongly as Kynan does). Anyway, now I feel like I've been doing something wrong I know Kynan though, I know he needs time to adjust and he likes to do the approaching when it comes to new situations and people rather than just being thrown into the middle of it all. But what do I do when it comes to appts like this? There's not time for Kynan to sit there for an hour or so to get used to these people before he has his check up. We have his 18m immunisations on Friday and I'm not looking forward to that. I really want to have the GP check the attachment between his top lip & gum but I know Kynan's really not going to like a stranger getting that close to him.