I do not know why you are not responding, but you are not charged per question, per response, nor per answer. So after I give you my answer, you can continue to ask me questions without additional charge until you are satisfied. I apologize if it is a site issue that you posted and the post did not go through.
I think I see what your questions are. Every family member including your grandchild would need a visa. You can look at the link below for all the information that you need on the visitor visa:
Essentially, they must have a valid reason for visiting, must have a way to support themselves without working illegally, must have significant ties to their home country, and must have the intent to return home.
A letter of invitation helps with some of this as it will help to show why they are coming to the U.S., how much time they will need and that perhaps they will have a place to stay so that they do not have to spend money. Usually you want to show that they are going just for a few weeks or so. If it is longer than that, immigration will wonder why and will become suspicious. They are almost sure to deny someone that says they want to visit for 5 or 6 months unless they have very strong evidences of everything else I listed above. So your letter should state why you are inviting them and that you will provide room and board while they are here visiting. But keep in mind that a letter of invitation is a small part of the process and isn't even a requirement (people mistakenly believe it is the most important) and it can sometimes be used against the applicant. For example, if the consular officer believes that the applicant will have too much support meaning that they could stay illegally in the U.S., the officer would deny the visa. Sometimes it is better to not even have a letter of invitation. The most important part of a case is to have strong ties to the home country.
Now as to some of the ties, they will need to show that they have significant close family at home, property not easily sold, and a good job for a good company that they have had for awhile that they would not normally abandon.
So if they are young (or old and retired or close to retiring), and without much money or any property or a good job, they would probably be denied. Immigration would see them as a risk for staying illegal. Also, persons that are planning to travel with their spouse and children are a risk as well because some of their significant ties are actually going with them.
I mean some people have been approved with less, but I am trying to give you the idea for the best chance.
As to how long they can stay, they usually would be given about 6 months. They are not allowed to stay beyond that time unless they file for an extension before their first stay expires. Even if they do, they would not be given more than 6 more months for a total of 1 years in the U.S.
As far as immigrating, the process is a long time for people from the Philippines, about 10 years or so, and no, they cannot wait in the U.S. as visitors during that 10 year period.
My goal is to provide you with excellent service – if you feel you have received anything less, please reply back as I am happy to address follow-up questions and there is no additional charge. Also, should you need to chat on the phone, private email or need help reviewing documentation, I am happy to do so for a small additional cost. Let me know if you are interested in these – I am happy to give you more details! If you have no further questions (at this time) please leave a positive rating for my service. I would sincerely ***** ***** You can do that by clicking on the 3rd, 4th or 5th stars or smiley faces if you see them. If you do not see any stars or smiley faces, you may have to scroll up to the top of the page or click on my name and they should come out. Also, your session does NOT close when leaving a positive rating, so you can continue to ask additional questions without additional charge. Thank you for your understanding.