It’s a bit of a pain for Boxing Day, because it looks like even though the tube is (mostly) running, the Overground on the former east London line, and national rail out of London Bridge, aren’t.
Nearest tube station to the ground is Bermondsey, which is best part of a half hour walk from the Den. That said, since you’re coming from the north side of the city, it might make it easier for you to only drive to somewhere like Wembley Park, where there’s plenty of parking, and then get the Jubilee line all the way south to Bermondsey and walk from there.
Your other alternative is to drive nearer to the Den and find an actual proper car park nearby rather than just a side street, although as someone who lives just across the river in a similarly dodgy-looking area, I should say I’ve found the bigger risks of on-street parking in London comes from Deliveroo drivers clipping wing mirrors, or over-zealous traffic wardens, rather than something like vandalism. And as others say, just don’t wear colours and try to park somewhere you think won’t be where most fans walk in the direction of, you’ll quickly end up by yourselves looking like any old pedestrians once you’re off from the main groups heading to the coaches or tube.