My Head Is Making English For My Mouth

About a year ago (give or take 3 months) I was telling Abel that he needs to speak Spanish.  To which he replied, "I can't, because my brain is making English for my mouth."  Whoa.  Let me think about this know: Abel is absolutely right.  Abel and Dina are awake about 14 hours in day.  They spend 8am to 5:30pm at their daycare, where they only get English.  They get home and we try to speak Spanish to them but this is what happens:

Me: "Abel que hiciste en tu escuela hoy?"
Abel: "Um, we had group time."
Me: "Ok, what did you talk about in group time?"

Pretty frustrating when I catch myself doing this.  When my kids first started daycare 2.5 years ago, Abel only spoke Spanish and Dina didn't really speak at all.  She understood Spanish perfectly well and had two teachers who speak Spanish fluently.  Naturally, Abel started speaking and understanding English sooner.  Even though he only spoke English to Rudy and me, he somehow managed to speak Spanish to Dina.  But, as Dina started catching on to English, Abel's Spanish left us forever.

When I try to point out that they need to speak Spanish,  I get two outcomes:

Me: "Dina/Abel tienes que hablar Espanol"
Abel: "I CAN'T!!!  I only speak ENGLISH!"
Dina: "But mommy, I do speak Spanish: agua, leche, cuarto, uno, dos, tres.  See!  I do speak Spanish."

At one point, I got really desperate and (I'm not proud of this) I increased their TV time so that they could watch Dora the Explorer and Go Diego Go.  Yes, I am a pathetic optimist (or naive, if you wish); no, I never actually though this would fix the problem, I just wanted to feel like I was doing something about it.  My next attempt will be this: raise enough money to visit my dad and my in-laws in Guatemala for a whole summer (not this one, too many things going on).