hello sara! how are you? the problem you are referring to is pretty much global in nature and let me tell you something it is far easier to teach adults than to kids! though i don't have any experience in teaching
kids per se but i'll give you some pointers see if they can help you!
apart from the above comment which without saying is helpful i'll give you some regular tested methods like playing songs which can be used in the classroom and singing these songs together with the kids(get permission for this if you have to because i know this would definitely help) ask these kids what they would like to do when they grow up and tell stories (simple one's) about these professions (which would mostly be like astronaut,police officer,doctor,musician and even cowboys!) tell them how this kid would go about doing things if for example someone says that i want to be an astronaut tell them about space the big big space stars rockets etc. remember kids will only be interested in what they like don't push them into grown-up business use small everyday verbs and adjectives to describe these things after telling them such stories ask them questions what kind of spaceship - a big one ( or any qstn or ans this is just an example), use english picture books drawings might help too if you are good at making them! stay relaxed through all this don't correct each and every mistake they make on the contrary praise them for making an effort! i would recommend some tv viewing of kid programs but i guess kids these days watch a lot of tv already so stay clear of that trap! ask them about their favorite animals,food etc
i can't think of other things right now but some golden rules which you'll have to abide by are-
when it comes to kids
don't sit on the chair too much, you have to be very interactive with them smile a lot let them see your million dollar smile they have to connect with you and be comfortable around you otherwise even the interested one's won't make an effort to learn! so move in the classroom let them feel that you want to play with them and did i mention smiling and making funny noises using of your tone making your pitch higher and lower!!
-D don't worry about them judging you they are kids if they laugh at you that probably means that they like you) use your hands to make and show actions again i must say be very interactive and don't worry about it too much it's just your first class and you have a lot to learn, be comfortable.
all the best for your future endeavors and let us know how it turned out..!