To deliver an item from my business to a relative?

[FunkyFriday]

I'm a cake artist. Haven't seen my grandfather since before Christmas in the small lockdown gap. His birthday is next week. My uncle has just ordered a cake for my GF so I can then deliver it, bringing my DC in the car with me thus allowing me to see my GF (from the driveway/him in the doorway) and for my DC to wave hello and sing happy birthday (again from the driveway.)

Legally I can make this trip as delivering for my business is obviously a legitimate reason to leave the house but I'm worried about neighbours reporting? Would you accept this order and take the chance to see GF? Or is this against the spirit of the rules? He's so lonely.

Yes it would be legal. I think it would be legal anyway as any adult cab meet another adult from a different household outdoors. In addition, if your GF has need for elder care, whether living alone or not, you can form a care bubble with him which allows indoors contact (but not the DC unless under 5? (Not sure on age limit, but there is one))

my uncle is his care/support bubble.

Care bubbles are different from support bubble. You can have multiple care bubbles plus one support bubble.