I fully understand and empathize with your predicament. mine are 19 months and 4years. Granny's dog is not great.
1. Ignore and turn your back on the dog when she jumps up
You as mum make YOURSELF top dog. If dog jumps up to say hello to your child, they turn away or ignore or squeak because they are excited, scared, confused, rather than you saying what most people would:
"Ignore the dog please! Get down. Get down!" etc,
Step right in (literally) to dog's space, in front of your child to physically move dog away with your legs. No need to say anything (if she doesn't know commands like "down" or "quiet", no point saying anything).
I'm not saying kick or hurt her at all. If you can avoid even looking at her so much the better.
She's a small boisterous dog, who's not really dangerous, just excited and confused. If you just walk forwards, into her space, she'll shift and that's a start to her realising you are in charge of your kid and she's subordinate.
I feel if your children are big enough, better for them to also just walk forwards like she's not there rather than them stopping, turning their backs which gives her bit too much influence over them. IYSWIM?
2. Only touch the dog when she’s being held and is calm (Er, never then....)
When on the floor. Small, nippy dogs on laps or sofas are notorious and much too close to kids faces.
If there's any chance you could get kids to meet other lovely dogs, would be good for them :-) Good luck x