From my experience regarding children, graduations, weddings, gifts, and such:
It is not your job to facilitate a relationship between H and the kids. It’s your job to just not destroy it.
Their relationship is their’s. Definitely be supportive of your kids’ decisions and choices. Offer your wisdom and guidance when/if asked for it. And gently steer, be a role model, a living example.
Son seems to have his mind made up for no contact with Dad over the summer until football starts back up. If he brings this up, I’d validate, and perhaps even inquiry into why. See his reasoning. Listen to his reasons (and/or feelings) for his choice. Just reaching out, not trying to alter.
I’d talk to daughter about her upcoming graduation. See what she wants. Pictures, supper, seating arrangement, father/daughter dance, etc.
Yes, family pictures will be a nice thing to have. If D wants to inform Dad of the schedule and details of the pictures, that’s fine. If she wants you to do that, that’s good too. You simply inform H of date, time, and place. Basically, setting up an appointment.
Joint gifts are yet another causality in the relationship strife. I’d not do joint gift giving. I get that it would be nice to maintain the same amounts and the joint efforts for daughter as it was for son. Thing is, it’s not the same. So, do the best you can. I’d give daughter the full amount. She earned it. (I’m surmising a smallish size pile of cash here. You did say - some money. I’m thinking like a couple hundred bucks.)
Whatever H/Dad decides to give, or maintain, or new traditions, or not, is on him. You do you. You do for your kids.
For big ticket items, for example, say you and H bought son a car before all this. And now you want to buy daughter a car. That would have a few logistical hurdles to overcome. A conversation would be necessary.
A new repetitive expense would also require a conversation to decide allocation of responsibility for each of you. It may be 50/50, it may not be. A lot of the bigger things depend upon the legal separation agreement set forth. The smaller gifts and such are individual.
Hope that helps.
D
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.