A.G.
My philosophy on protecting kids from germs is, for the first 3 months everyone MUST wash hands and the baby is pretty much homebound. The nest three months, now that their bodies can better handle getting a cold or some small bug, only people who have been at a school or anywhere with a lot of random people must wash hands and the baby goes out once or twice a week but with cleaning up anything that strangers have touched before you. Up to and including this point no random stranger can hold my baby, and personally ever. I think it's rather impertinent for anyone to even ask in the first place.
After that I let the baby continue to be exposed to more and more things to strengthen their immune systems so that they are introduced to each new things in somewhat small increments and this way their systems can handle them. I have done this with my son and not only does he rarely get sick but when he does he handles it very well and gets better very quickly, I haven't once needed to take him to the doctor for an illness.
As to your mother, I have two rules that have served me very well, first is that it is a grandparents prerogative to spoil their grandkids and I let anything go in that department, I also trust them to do just fine with the kids when they babysit; if you don't trust that she'll do a good enough job then DON"T have her babysit, period. My other rule is that if you can't respect my wishes in my own home then you can't be in it. That doesn't mean that you cut her out of your life only that you only meet on neutral turf. Anyone that is that disrespectful shouldn't be allowed the privilege of being in your home, and it is a privilege not a right. My sister has rules that are much more strict than my own but not only do I follow them in her home I try to make some allowances in my own to support her in how she wants to raise her children, for example she does not watch ANY TV or movies on Sundays, so when she comes over with her kids on a Sunday I try to keep any of that in another room but only within reason. And because of my efforts she is very supportive of my methods.
My last piece of advice is to NEVER EVER let someone guilt trip you into anything, a guilt trip is just one of many ways of manipulating someone and whenever someone is being manipulative it is because at that moment their agenda is more important to them than you are. Remember that and respect yourself enough to put your and your families needs before anyone else's selfish agenda.
Good luck, enjoy your trip doing what you will enjoy while making some reasonable compromises, and in the long run everything will work out, it always does when you stick by what you know is right for you and your family.