I have a little different view than most parents, but it is probably because most of my family are missionaries and have raised their families abroad. Some countries nurse their children until they are six! Yikes! I'm certainly not suggesting that, but putting it into perspective, it tends to be more of a cultural preference than a health issue.
Americans seem to be over concerned about weaning their children from bottles, pacifiers, security items, etc. and potty training them as soon as they can walk practically, or fighting with them for an hour to take a nap at noon when they would naturally fall asleep at 1 p.m. Instead, why not let them lay themselves down a 1 p.m., save an hour of fighting and still get in a peaceful nap minus an hour of struggle?
That being said, the real deciding factor should be what brings the most peace to you home and what issues are truly important to you and your family and not what other parents are doing with their children.
Being a mother of five (soon to be six) very spirited and outgoing children, I had to decide if an issue was a "hill worth dying on" so to speak. There were so many important issues to tackle during the day that were non-negotiable health/safety rules (light sockets, poison, running the the road, etc.) that would not be altered that when it came to things like whether or not they had a bottle or were potty trained before they were two, I left those to their preference. My rule was that the bottle had to go before they went to kindergarten/pre-school and it always did and they let it go on their own in their own time and I was left with the peace of not having yet another issue to fight about in the midst of so many other important ones. And, no, none of my children had any dental problems from having bottles before naps and bedtime.
To me it was more pressure from other parents than a strong personal preference about which device my children received their beverages from.
It was the same with potty training. I went through torture for a year and a half with my first two trying to keep up with other parents' unwritten timeline. Finally I gave up. A few months after I quit fighting with them they came to me and said they wanted to go potty on the toilet from now on and that is what they did. That was easy! I got a clue with the other three and waited until they were ready and viola! It took just a day instead of months and months of stress and upset. They were all potty trained sometime in their third year with no stress because they were ready instead of being forced.
I hate to be so long winded with examples, but I am hoping they helped to let you know that what other people do is not anything you need to worry about. You have already one through more trauma than most parents have had to experience. My suggestion for you would be to decide if this really is important to you personally and why, or if it is something motivated by external pressure. Then it may help to weigh the cost of all of the stress at nap and bedtime. I am completely not judging whatever decision you come to. We certainly don't let our children rule our parenting by whether or not they throw a fit about our decisions. I am just suggesting that you really weigh if it is your "hill worth dying on;" and it may be.
If you find that it really is something it is still that important to you, then just coming to that conclusion with clarity can strengthen your resolve to endure the retaliation you will receive as you help to wean your child from bottles. Just making the realization that this is something that you have decided for your family and not something others are pressuring you to do can make the resistance from your child much easier to manage with determination and calmness, especially when Grandma is looking at you with big sad eyes saying, "Oh, one little bottle couldn't hurt that much, could it?". Don't let fits or sympathy sway you from the decision you make as Mother! Believe me, my kids' Grandma is the best in the business! :)
On a side note, something that has worked for me and may help with the transition is to allow them to have a bottle all they want but only with water. They can have other beverages in a sippy cup or regular cup, but bottles are for water only. They may lose interest eventually just based on that and may even want to still take an empty bottle to bed. Sometimes it's just chewing on the nipple that causes them to relax and sleep, not necessarily the beverage, and they will eventually give that up, too.
On the other side of the equation, if after examining why weaning is important you find that it is not really that important to you personally but important to others, that realization can also help strengthen your resolve when people in public ask why your child of 3 or 4 has a bottle (not that it is any of their business). I would just look right at them, smile, shrug my shoulders and say in a really casual way, "It really doesn't matter to me which device my children use to drink their beverages!" like it's totally no big deal and if you say it like that, it won't be a big deal to them, either, (Or if it is, then they have their own issues to post here on the board!) :)
I hope you find the very best solution for your family and that your decision is led by personal peace and not external or cultural pressure. I sincerely wish you the very best!