Am I overreacting?

Back story: My SO and I have been together for 3 beautiful years. I have 2 children from a previous marriage and my SO has none. I share custody with my kids dad and have them half the time. So half the time I stay at my home with my kids and half the time I live with my SO at his place. We are currently looking for a larger home for all of us to live in together.

So, my partner has his own business and is in business with his best friend. They spend every day together working. And they usually work Monday - Sunday. No days off. However, today my SO informs me he is taking the day off so we can go out on the boat! I was sooo excited. We had breakfast and then his biz partner calls and says they have to go pick up a wheelbarrow. No big deal, I go to the store and get things for us and come back home. The issue is- they left to get the wheelbarrow at 10:30am!! It is now 12 and they have been back for over an hour and are just sitting together! First playing on their phones for awhile and now they have moved to the living room to watch tv! They don’t even talk! Just sit in silence for most of the time. I am sitting in the bedroom (in my bikini) fuming. I texted my SO to let him know I wasn’t happy and he said for me to come in there with them and his friend would leave soon. I am LIViD! We are together maybe 3-4 days a week and that’s it. He sees this friend every single fucking day! I know he “feels bad” asking him to leave because he is like that but holy fuck, MAN UP. It is so rare we get an entire day together and now this shit???? I don’t wanna leave and fuck up our entire weekend together so I’m literally just in our bedroom trying to keep it together but I feel sooooo hurt. Our relationship is amazing and we did spend all day together yesterday but little things like this make me wonder! Would you be mad?