I enjoy the younger games, as it offers a chance to interact/educate while I ref. When I coached, I often saw newer referees that were nearly silent on the field - and the kids often had no idea what the referees were calling or why - even on simple things like throw-ins.
Now that I referee (and I'm a new ref too) - I'm pretty vocal when refereeing - calling "Blue ball" when raising my arm to indicate possession helps them understand what's going on. Saying "hands down #7", when you let a little contact go will probably help when you whistle #7 for a foul the next time they do the same thing. I'm often saying "play, play" when two players come together, as they both might think they were fouled, or that they fouled the other player.
When play is stopped for injury, I may ask the kids if they know what the restart is - many don't - so you can explain the dropped ball restart to them. This has the advantage of making you more human too - not merely as Olivia says - just a uniform.
You're definitely going to have players/coaches/parents unhappy with your calls - and know that some of it may be downright manipulative - trying to get you to change calls, or give calls in their favor later. I'm vocal with this too - I'll call "no, no - blue ball - off red's leg" if a red player picked up a ball to throw it in.
One other item - in both cases you said things started well. You might be finding that by letting marginal fouls go early that you're signaling for the kids to continue to push the envelope to see where your limit is at. Making some early calls on marginal fouls will nip that in the bud, and set the tone for the rest of the game. It's a lot easier to stop the marginal fouls early than it is to try and rein the kids in later in the match when it's a bit more tense.
By the way - you're ahead of most of your peers, as coming to forums, etc. to get input/support means you care a great deal about your performance on the pitch - well done!