That's great, good for you.
I agree with Joyce, good having Boomer meet this boy where he is which is a neutral setting and also agree with her advice about taking them for a walk prior to bringing him into your house.
He may adjust right away, if not, it might take a few days even up to two weeks.
Both of my dogs were adopted at the age of two-my girl had never been in a house before and wasn't house trained. Worked with her for a few days, took a full week before she stopped having accidents in the house which was only two. My boy fit in right away as if he'd always belonged, he didn't need any time to adjust at all.
Each dog is different, so you'll want to take each day as it comes. You may see this boy settle in right away or it may take some time before he relaxes and feels like he's home.
There's a lot to be said for adopting an older dog or a young adult, you pretty much know what you're getting. You may have some things you want to work on or some training you want to do with them. You are past the puppy stage, usually house breaking, and destructive stage, all you have to do is enjoy them and have fun.
Be sure to give them each their own one on one time with you and you might want to feed them seperately the first few days to be sure there is no food agression problems.
Hope the meeting goes well, looking forward to seeing pictures of him and hearing all about him.