On our trip last month, my son requested to go there, so we went. I'll admit, I wasn't thrilled that he chose that restaurant because it's always been a bit disappointing. HOWEVER, I'm glad to report that I was pleasantly surprised this go around. It really was a far better dinner experience than I remembered it being previously.
First and most importantly - wonderful margarita! I drink classic margaritas on the rocks and this was right up there with one of the better ones I've had (and I've had a lot, LOL).
I'm not sure if you have kids young enough for a kids meal, but their kids quesadilla meal was really great. My son loved it. We eat at a lot Mexican restaurants and this meal wasn't your standard kids quesadilla meal. Although, if you have a picky kid who wants a typical quesadilla and balks at something that looks different, you may have a hard time with this. It looked almost like a taco because it was so thick. Basically, one tortilla folded in half and absolutely stuffed with shredded chicken and cheese. It was probably 3/4 inch thick at least. And the meal was served with rice and fruit. He also had a fruit smoothie as his drink/dessert.
I had the Plato Mexicano - beef tampiquena, chicken enchilada, beef flauta, black refried beans, Mexican rice - and it was very yummy. Way more food than I could possibly eat, but I tried some of each item and it was all good.
My only complaint is that the chips are bagged chips. But we ordered a side of guacamole to dip them in and that helps.
Your DS will definitely get a chance to practice his Spanish. My DS (he's four, LOL) knows some Spanish from his teachers at his preschool and he loves impressing all the CMs around the Mexican pavilion with his Spanish. They all are quite enthusiastic about speaking with him and letting his practice some of his words.
Edited to add: We went there in 2005 when DS was still allergic to dairy and I don't remember it being a problem to get him a meal without cheese. I can't remember specifics right now though. But I don't think we called ahead and special ordered or anything. I know they have steaks, etc. on the menu and you could just get that with rice, beans, etc. - no cheese.