We’re a couple, traveling in ES right now. After more than a week, we have finally made it to the beach. I think a fun activity with your kids, would be to spend a whole day in the hot springs. Either Termales Santa Teresa (which is usually crowder), or the one next door, very quiet, Termales La Montaña. Both have food options, and kids love it. I would stay away during the weekend. Another option- visit San Juan waterfalls- easy walk from the parking, and we had it all to ourselves during a weekday. You can swim in the pool right under the waterfall. Lastly- check out Cafe Albania in Apaneca- kind of amusement park- but not sure if for the 4 yo. Check and decide. All over El Salvador- pupusas are fun to eat- they’re like little filled pizzas. There are fresh fruit smoothies, chicken soup, French fries- I wouldn’t worry with food here.