Norman, I understand your concerns. I mentioned in in another post of mine a few weeks ago, that Dad got to the point where he could not eat sandwiches because he seemed to 'forget' the concept of picking the whole thing up together but instead kept picking up the bread on top and then made a mess of the rest. He also started continually using a knife upside down and eventually it got to the point that he couldn't use a knife, fork or spoon very well at all. These days although he never uses them anymore I see he still often does the hand motions of using them, but when i give him a utensil he can't aim it right at the food, the plate nor his mouth. Drinking from a cup was the last of these skills to go, I used to take so much delight in seeing him being able to use one!
But I digress, in answer to your dilemma it can be addressed in some ways by planning ahead and trying to think of meals that can be acceptably eaten by using the fingers. Chips and 'nuggets' (chicken or fish battered but in small finger size bits) are good ones, for flasher meals a lot of seafood is acceptable to eat with the fingers (you may have to shell things first or ask for them to be out of their shells). Even just by avoiding gravies and sauces it can be not too bad eating things like steak and chicken 'steaks' with the fingers if you just ask for it to be cut up in small pieces before it is served, or cut it up yourself when it arrives at the table.. Think 'pieces' with veges and avoid mashing and overcooked items. Grapes are great, bananas can be okay because the person can hold the bottom with the skin still on and eat it without getting the food all over their fingers (although eventually Dad began not realising that the skin was not edible as well!
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Also I have learnt to avoid biscuits that have toppings that melt as Dad when he could hold them would often do so for a long time and squeeze them before getting round to putting them in his mouth. Take your own desert of hard lollies, biscuits or have cakes that are less prone to falling apart like carrot and banana cakes. Spoon foods are often less challenging then knife and fork foods at first too, so desert may still be alright.
We still like to go out for a meal and this can cause problems, where again people may not understand a little mess on their tablecloths
Lastly, I think you just need to get to the point where you don't care if people are 'not understanding'. Of course you can explain to restaurant staff at first and that discreet card I have mentioned before is good for doing this without embarassing your 'dementia' sufferer, or mention it over the phone at the booking, even ask for a table that is a little less out in the open. But basically I recommend taking the attitude that if folks don't understand that is their problem, we aren't going to fix it by hiding our loved ones away, if they saw it more often they would get used to it, and if society was more used to it, life would be less difficult for people like us and other dementia sufferers, or even others with disabilities. Of course you are probably concerned about the dignity of your loved one, but try to temper this with the realisation that neither of you have anything to be ashamed of and instead you are setting an example of what society should accept and respect. If your other half is greatly distressed by others looking at her, then of course you shouldn't force her into that situation, but a lot of times I found that we were more distressed than Dad about the whole thing.
Preparation, preparation, preparation is the key. Think about what foods can be acceptable, take cloths or wet hand wipes to stop greasy fingers leaving their mark everywhere. I guess it is similar to what a mother does when she takes her 5 year old out with the rest of the family to dinner.
Try not to be distressed by what others think, they have no concept and our 'sufferers' should not be forced to be second class citizens because of a few poorly brought up folks. Well brought up folks know it isn't polite to stare and that one should be understanding, it is only rude folk and people incapable of understanding (like children) who will make life a bit more difficult, and this can be alleviated if one ignores them and carries on enjoying the meal with your loved one.
One last thing, try to keep the eating skills up at home as long as possible by not immediately helping your loved one to eat their food, providing utensils even when they don't tend to use them much anymore, and if you must help then put some of the food on a fork and hand it to them to let them try first to eat it from the fork, or cut up the food into pieces that are more easily manageable. Be confident that you will 'know' when it is time to step in, when they just can't do it anymore. Try to remember the 'use it or lose it' adage. Don't make a fuss of dropped foods, don't make a fuss about messes, (one gets quite skilled at not fluttering an eyelid!) show with your attitude that your loved one has nothing to be ashamed of, they are just a person doing the best they can with what 'God' has given them to work with. Even show admiration that they can do so much considering what 'God' has taken away from them.
Be proud.
Hope this helps.