How do you keep baby away from sick siblings??

My 2 year has a cold (cough lots of mucus, runny nose) and it’s so hard keeping her away from her baby brother he’s only 6 weeks I don’t want him getting sick since he’s so small 😭😩

And my 2 year old doesn’t understand that obviously it’s just so hard!

Any tips!??

Also any tips on best cough syrup for a 2 year old that hates medicine? She has no fever so I was waiting to take her in to see her Dr. but want to give her something meanwhile unless she develops a fever meaning she probably has an infection and would need antibiotics

Oh how I hate the cold and flu season