booster jabs at 3.4 years

[WoTmania]

DS1 is going to get his booster jabs next week. It took over a year after his MMR to get him into the nurses room without tears.
How did you go about explaining it to your DCs? I don't know whether to explain (an how to explain ' a nice lady is going to stick a needle in you arm and it'll probably hurt' isn't really going to help is it? )and risk the anticipation making it worse or just spring it on him.
WWYD?

I didn't tell DD when she had her's last week, the doctor said she was going to put some medicine in her leg. They do it so quickly and it's over so fast.

And I whipped out a carton of Innocent and some buttons straight away

I was considering the chocolate as consolation. I'm being a wimp and making DH take him in as I'll have DD in the sling and won't be able to hold him if he really struggles.

Take something to distract him immediately and he'll forget about it I'm sure. It's only a scratch.

DD had horrible cellulitis around her eye recently, and taking her to the doctors for her to 'pop' the very final white head bits of it, just under her eye, while she struggled wildly, was infinitely worse. The doctor asked me if I'd like a lollipop too! (To which I replied that I'd rather have a vodka )

I was really stressed about taking DS2 for his booster jabs. I told him we were going to the docs to get some medicine to stop him getting poorly.

They offered to do the jabs in the arms or legs, but said arms were generally less painful. I asked DS2 and he chose arms. He sat and watched them do it, then got off my knee said thank you and was off out the door.

I gave him lots of praise (and some chocolate buttons) for being so brave. I was completely expecting struggling and tears, but he didn't seem bothered at all.

Good luck WotMania. I'm sure all will go well.

Thanks. He just hates going to see Drs. Just having his chest listened to elicites screaming fits if is in the wrong mood . Will just try not to worry.