Rambling is good
Sometimes we just need to get it out and that's ok! Yes, they are better when you can keep them busy physically and they don't have the time to sit and brood. Their brains don't function well and don't multitask well. Keeping them engaged is the best... but we do wear out ourselves. Just be glad you have a kind neighbor that is willing to engage with him and give you a wonderful break! That is a priceless blessing!
I hope his birthday celebration goes well. Keep it small and quiet keeping as much of his routine as possible. Let the kids join him rather than expecting him to join the kids and it will work better.
Don't rush what is coming... do what you are doing and enjoy the moments you have with him now. Know it will probably not come on suddenly but over time. Good days and bad days are the norm. As time goes on the good days are not as good and the not so good days are a little worse. That is just how this disease progresses unless there is a traumatic or medical event that creates the rapid decline.
Please keep the sense of humor and the ability to laugh. Take something not quite so funny and turn it into humor. Keep your smile and he will be more likely to have one as well. Laugh and he will follow you. Just today Mom ask about her Mother. I know from her past that she and her Mom did not have a good relationship. I just looked at her, smiles, and said ..."Why would you want to go see your Mom?!" Mom actually broke out in a huge smile and said... "I don't!" We both laughed. In that small moment I actually had my Mom back. Just a brief moment but it is one to carry with me because there are not many of those these days. So even something negative can be a laugh moment.
I hope the good days continue and are at least more frequent than the not so good days