I've some inquiries regarding the US Visa.?

yes, it's possible but you'd have to work out the various interview dates with the consular section to make it all work. If you and your husband are approved, you can go without your children or with the two of them and the other can be interviewed later in what is known as follow to join status. if you go to the US first, the immigrant visa officer will want to see proof of that. If you can't get their attention via email, talk to them directly about it at the interview.