I'd defo do a separate jab - mince pies and Xmas pud are HUGELY carborific so if you were to jab including that before your whole meal you'd quite likely fall off your chair hypo before you'd finished your dinner. Well - I would anyway - I mean it's roast beef this year (none of us is that keen on Turkey TBH) so there will be small individual Yorkshires(I only have 1, so 5g) small chunks of potato roasted (so about 2 make 10g, I usually have 4 or 5 of them, say 25g) and sorry No 1 daughter the trained chef, but honestly her roast parsnips aren't the best - all crisped up and no soft inside cos she cuts em too thin for my liking - so I'll have just two or three probably but being so 'well done' they aren't such high carb so that's only another 10g at most. (Just one piece done as I like it done, would be 10g on its own!) (and I'd have at least two!) None of the other veg (at least sprouts, carrots and peas) have that much carb anyway - cos with enough roasties I certainly won't bother putting any boring mash on there thanks - a few in the carrots but with everything else on my plate, I'll want one tablespoonful at the most. Not that much in gravy really TBH - we all like 'coating' gravy and you don't have like a half pint of it!
We often find we need a rest between dinner and pud anyway cos my daughter's dinners are pretty huge all in all - PLUS she always does a starter - this year it's a slice of melon and antipasti with all sorts of meats including parma ham. So you're usually ready for a bit of a rest by that time anyway. And what I add for the melon entirely depends on how thin she cuts the slices doesn't it? Will she use a whole Honeydew melon for 6 of us or just half? Doesn't matter really - about 15g if it's a sixth of half, or 30g if it's a sixth of the whole one - unless it's a small Ogen melon to start with which would proportionately make the values just a bit smaller.
Hence - assuming my BG is around 5 or 6 somewhere before I start, I'll jab after the starter and before I load my plate with my dinner once the veg dishes appear on the table so I can see how big the individual bits are and assess how many/much of each I'll put on my plate. That insulin will need to start dealing with the melon cos that will have got there by the time the insulin starts being of any use and that will keep it busy till the contents of the main course starts turning up.
Crème brulee is on the menu again by popular request so my one will be about 10g but I understand there will also be a (cold) chocolate mousse appearing and if I like the look of it and decide to have some I'll have to discuss the contents with herself. However - she'll more than likely calculate the carbs for me herself while she's making it if I know her! They learned all the things like nutritional values in ingredients and therefore complete recipes and complete meals etc at catering college in those days of course (just as you had to then to get your Cookery O level) and I should imagine the photographic memory comes in pretty useful for stuff like that, shouldn't you? LOL God alone knows who she inherited that gene from!