Playing Heroes of the Borderlands, Players' First Playthrough, 1st Time DMing

I played a lot as a kid, and now I'm playing with my kids.  I've tweaked the basic game that came with the boxed set slightly and noticed something.  When the combat maps come out, the game really seems to shift to feeling like a board game and the kids' imaginations start to turn off.  Anyone else see that happen?  I had added catacombs beneath the temple in the keep and we had no combat map for that. I  had made my own map and kept track of movement on that, and described what the characters saw as they moved along, and sketched out on regular paper a basic layout of the map as the characters moved.  Then we just did theater of the mind for combats - and we used basic minis to show general positions of the combatants.  That seemed much more immersive than when the characters have been at the caves of chaos and we've used the provided combat maps.  Anyone experience this kind of thing? 

I guess it depends on what aspects of DnD you like.  But the difference seems pretty pronounced for us.  The kids are 13 and 12.

I think it depends on your players/how much you rely on the map for descriptions. My table LOVES a combat map, but I give descriptions and get them hyped about the layout before even bringing out the map, so the map gives them a visual to what I was already describing. That being said, I don't use pre-printed maps because I love creating 3d maps with terrain pieces and stuff. So I get them super excited about the map, then drop the map I've spent time creating, and they love it. And I let them interact with it...they control their miniatures' movement, they can interact with the terrain pieces as long as they don't like, move my trees around or something, and it doesn't really give "board game" vibes. I still use theater of the mind techniques even with my map on the table, describing what they see/hear/feel/etc, because the map is just art that I like making for them to play with but I still want all the other senses involved to keep them immersed. I have a bunch of basic grid mats I use for unplanned combat and I'll do exactly like you did with drawing/descriptions, and the only difference in the feeling of combat is my players have less stuff to touch.

If you're just putting the printed map on the table without any fanfare, they're probably feeding of your energy. If you seem excited while giving descriptions and drawing maps live during the session, that's the energy they feed off of and might be getting more into it. They need you to create something immersive in order for them to be actually immersed. So even with the printed maps - give the descriptions, use the theater of the mind techniques - the only difference is you don't have to draw, and your players might be more immersed/into it. 

With somewhat younger audiences it takes a little bit more to get them going. Like DNavarette0819 said, it's all about the presentation of it. Don't drop down a map and then say roll initiative. Hype it up! Give them some cool description, lay it out, and keep the energy flowing.