Well, on one hand I do really like Seaworld. The very first time we went, we hated it for a couple hours, then finally decided to see the Pets Rule show, and our whole day turned around. My childfree brother and SIL got passports and go often just for that show on SIL's lunch break (she works in downtown San Diego). We've been a few times since, and really enjoy it.
In fact, our first time there, we went two days to SW, and only one day to DL!
However, we regret that now...just didn't know how big a fans we would become of DLR.
My point is, though, we're fans of Seaworld.
But I would NOT cut a day off of such a short trip to do that drive and go to SW then have to do that drive again. My brother learned to drive in Miami FL and he's lived in so cal long enough that he's used to it and doesn't see any problems with the so cal traffic. While Seattle area traffic is weird and people seem to lose their brains routinely on the road...at least we're not going 80+ mph while doing so, like they seem to do on the drive between San Diego and Anaheim. I do not like that drive! I have lived in CA, I drove routinely around Washington DC, I've done the drive between northern VA and northern SC a million times...and I'll drive the beltway 100 times before I want to drive to San Diego again. So just for one day? nope.
Now if you had a longer trip...if you were leaving from San Diego...if you took the Surfliner down and then the Amtrak bus to the SW stop...then I'd consider giving my OK.
ALL THAT SAID! If YOU, the adults, want to go to Seaworld, then by all means, DO it. Just don't do it for her (that goes for DLR, too, by the way...my son does have memories still from our trip at 2.5 (the 1 day in DL, 2 SW days) trip, but that trip was for us, not him.).
And check for ticket specials online (on Seaworld's site). Sometimes they have % off a one day, sometimes they have "buy one day get another day", sometimes they have "buy one day get the rest of the year"...so if you might be back in that time, it could be worth it.