Wow, you have a challenge on your hands! Your experience sounds very much like my first teaching experience. There really is no way round it - it's going to be tough. I do, however, have a few suggestions for you. I hope they are useful.
-Language. I understand that the school wants you to use English as much as possible, and I support that. The only way for students to learn English is to hear it and speak it. However, I think your Spanish skills will really be useful here, especially for classroom management and giving instructions. I would suggest giving all your instructions in English, repeating them in Spanish if students seem confused, and then saying them in English again. That way they are still getting a lot of English exposure but they will also know what is going on.
-Lesson plans for each grade level. I wouldn't worry too much about trying to make all your lessons separate. You can often use the same lesson plan for K, 1 and 2, but expect more from the G2 students in terms of language production and rate of learning. It's hard to know without knowing your students, but as a general guide I would suggest songs, story-telling (you tell the story) and play-based activities for K+1, and some writing and story-telling (they tell the story) for G2 and G3.
-Game ideas and story ideas. Think back to your own childhood. A lot of games and stories are very universal and children might be familiar with a variation of them. My Korean, Thai, Saudi and Russian kinders were all familiar with 'what's the time Mr Wolf', clapping games (such as 'a sailor went to sea sea sea, to see what he could see see see') duck duck goose, simon says, traffic lights, telephone, I went to the zoo and I saw....(memory games). If you are able, talk to the local teachers and ask them what games or stories the children know and like in their native language. Then you can just translate them into English and use them. For stories, I often stick with traditional tales. Do you have a chalkboard or paper? You could tell some traditional tales or fables, draw the characters (or have the kids draw them) on separate sheets of paper and then retell the story as the kids act out the parts of the characters. For older kids with some English, you could do a reader's theatre where you read the part of the narrator and they read the lines of the characters. You can practice this over and over which helps their fluency, pronunciation, and confidence.
-Learning expectations. Just keep them really simple. Better to exceed expectations than fail to meet them! For K-3 I usually use statements like 'students will be able to name some animals' 'students will join in with a song' 'students will be able to write some adjectives to describe themselves'.
-Limited resources. This will be your biggest challenge. If you can get some paper it will really help you out. Otherwise you are really limited to songs, games, chants, poetry, listening to stories. If you have a watch, phone or egg timer and students can talk a bit, you can have them take it in turns to talk to the class for one minute each. My kinders used to like to see how high they could count in a minute, how many animals they could name, how fast they could recite the alphabet etc. My older students like to talk about themselves and their families.
-Assessment. It's really hard to asses students with very little English and very few resources. I would suggest making a list of words they know around a certain theme at the beginning of the week, and then retesting them again at the end to look for improvement. So for example you could give them a sentence frame 'I like -------' and see how many words they can come up with to finish the sentence. If they get more words at the end of the week - success!
I wish you all the best - let us know how it goes!