Old Town is great fun (and only ten minutes from where I live). Kind of a pity you're down here during our heatwave, though. It's usually about ten degrees cooler.

If you have the time, you might enjoy taking a trip up to the old Cabrillo lighthouse and to the tidepools here on Point Loma. It's something like $5 a car to get in and the views are not to be missed.

Tips for SeaWorld which you probably already know: Bring a carrying case with your own bottled water and snacks (pricy things in the park itself), and arrive as early as possible to get the best seats for the dolphin and whale shows. I like to take a book and get in right when they start seating. Also, bring towels and possibly changes of clothing in case your girls can't resist sitting in the splash zone. If your budget can take it, the restaurants are fantastic, but that's another reason to bring your own snacks.

Whatever you do, don't forget the sunscreen, and apply it religiously every fifteen minutes. I don't know what it is, but the sun over SeaWorld is particularly strong, so also keep an eye out for signs of heat exhaustion.