Hi Nick, I would put S's Bday first and your sitch second here. The tramp is for him, and I don't think there's any problem helping with that. It's an act of love for him.
As for the meal, I would carry on with that lovely family tradition. Your W can link in if she wants to - if not, I'm sure you'll have a lovely time anyway.
Hope he has a great day!
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus