Is there any problem proceeding with the early entry application regardless as long as you don't lose your daycare spot? January is a long way away in developmental terms so while your DD may be happy now, her needs may change dramatically in the next few months. Would she be going to school with her older friend from daycare if she went to school in January?
Early entry seems one of the easier forms of acceleration and perhaps simpler to arrange than a direct skip to first grade which could be needed if you stay in daycare next year.
I am not sure why you think that being correct age for grade will help with the high school entry? If it is an assumption that she is more likely to get high scores in the entry exam because she is older then that is not necessarily true. We have found the opposite. Much better test results that occur after acceleration because the material is more appropriate and engaging. It's hard to focus on what is very familiar and easy.
The most important thing we have found for general happiness is an appropriate curriculum. The social side always seems to improve if we get that bit right as we end up with a happier more confident child. But every child is different.
