I don't give out specific HP or AC numbers to my players.
TL;DR I don't personally like giving out HP or AC numbers, since it takes me out of the immersion of the game, turns it from a narrative storytelling game into a tabletop battlegame. However, it's your game and you should do whatever is the most fun for your group.
Personally I don't give HP or AC (Armor Class) numbers out to my players, but because of the nature of the game they usually figure it out within a couple rounds anyways. If they hit with a 15 but miss with a 14, it doesn't take a genius to tell you the AC is 15.
Narrative Clues are Great!
One thing I see a lot of people do that I really like is giving narrative clues as the combat goes on. Going with the 15AC example, a player who rolled a 15 to hit would get a description of their character swinging in and just barely catching the goblin in the arm as he tried to sidestep the character's strike. A 14 to hit would likely result in the strike landing but narrowly missing the chink in the enemy's armor and bouncing off with little to no effect (AKA a miss, since the AC is 15.)
Another thing I like to do is carry over the "bloodied" system from 4e, where the DM will generally hint to the players that a creature is "bloodied", "not looking so good" or etc once it goes below half of its maximum HP so that the players get a general sense for how the combat is flowing and how close they are to killing the enemy.
This strategy works for hit points too.
The DM can also provide context with his descriptions for how much the strikes appear to be hurting the creature. A fighter who does 5 damage to an enemy with 100HP would find the DM describing how the creature seems annoyed by the attack, similar to how a human would be annoyed at being bitten by a small cat.
Conversely, a wizard that blasts an enemy with a fireball that does 48 damage out of the enemy's 50 total HP gets a description of the enemy barely remaining on their feet, singed from head to toe and covered in burns so painful it looks like they're having trouble staying in the fight, swaying left and right as it steps in for one final halfhearted swing with its longsword.
Of course, it's the nature of D&D 5e that you get to choose how you want to play the game. If you want to tell your players the remaining HP and AC, it's your game and nobody's stopping you. Do whatever is the most fun for you and your group. Talk with your DM and the rest of the group, discuss your feelings and ideas, and come up with a solution/agreement that everybody will enjoy.
Also take into consideration that you're playing the game with kids, which changes the dynamics a bunch and is something I have zero experience with. If you need to change the system up to appeal more to your target audience (your kids) then I would say definitely go ahead and try it! You can always try something, see how it works, and change your mind later if it's not working out.