London Day Trip Tomorrow. Parking? What to See?

[Fifteenthnamechange]

I'm thinking of me & my DH taking our 3 & 4 yo to London tomorrow for the day for some festive fun.
Firstly we're thinking of driving to reduce cost. So my plan would be to drive & park near West Acton tube. Last time I went there on street parking was fine (ie not all residents parking). Anyone know if I'll still be ok to park there?
Then I was thinking of going to South Bank, maybe Thames clipper ride.
Any other free/cheap Christmassy things to do? I'd love to see Carnaby St but I'm worried it'll be crazy busy.

Hi in the borough of Brent certain parts have free parking when there isn't an event happening. So I would check there.
Then you can get the tube or bus into central London. I commute daily from there into Nottinghill and have also got the bus from there into Edgware road and Oxford st.
By Oxford st there is 'Winter Wonderland' which is really fun.

Carnaby Street is a deathly dull pedestrianised street of the usual shops you'd find in any high street.

Everywhere in London where there is shops will be outrageously busy.

Stick to Southbank (also busy but not so much as Regents St area). Clipper boat yes.

Most of the fun things are going to be manic, so I wouldn't rule things out based on how busy they are - it's just that time of the year, and the last Friday before Christmas! It's busier after lunch at the moment, as people are finishing early.

Carnaby street is great but will be busy; might be worth carrying the little ones. Winter Wonderland can be fun, if it's the type of thing your kids will enjoy. It tends to run pretty smoothly even when it's busy. The general Christmas lights are gorgeous when it's dark!

I've been working in London for the past few weeks, it does feel lovely and festive but man it's busy

Thanks for your comments.
I think we will swerve Carnaby-I just wanted to see the lights there. And have a nose in Liberty, but in reality it's too inducing.
The good thing about 3/4yo boys is they are easily pleased with trains, buses & boats.
So may head to the Tower (via a photo with Paddington at the station) then head to South Bank & see how that entertains them