Lord no, I'd never travel that far for it.
As PPs have said, if you live nearby to be able to go to London for a day trip, then it's OK, but I wouldn't travel especially to go.
We've been twice, the last time in 2019 just before Covid.
We got there for opening time and had pre-booked the big wheel. There were lots of good rides (Munich Looping is excellent), but so, so expensive. ML was £9 per ride, and no other ride was under £5, mostly £7.
There are other things to do like the circus and ice skating, but everything costs ££.
Once it hits around 4pm the crowds are unbearable and you can't move. The queues for overpriced food and drink were so ridiculous we left and walked up Oxford Street and found a restaurant for dinner.
Depending on how much your DS would want to do, you'd easily spend another £200 there.