a big problem in this entire system is sometimes the elderly aren’t completely clear minded. That means they may not remember mow is coming “today” or within any time frame.
presuming the delivery is prearranged, the trespassing sign is moot. You have been invited to enter for the purpose of delivering the meal.
the bigger problem is the beware of dog sign. You got lucky with this one. I have known dogs that were more or less silent until they attacked. If such a dog was outside you would have been bitten, maybe worse. I would hesitate to enter any property that has such a sign without the resident being present. Too many possibilities.
As far as welfare checks: it’s an honorable intent but unless the resident is aware of the possibility of you entering the home at the actual time of entry, well, I’m surprised nobody has been shot yet. Some elderly are quite protective of their home and may shoot somebody entering their home. I realize you knock but it’s possible all that did was wake them up and they never heard you announce who you are until it’s too late.
While meals on wheels is a great service, there has to be some specific details worked out with each recipient as to any details neeeding to be known at the time of delivery. No delivery person should be getting bitten by a dog, or worse.

