Hi Lindsey,
Always a pain to have technical problems, I know.
I like Saludos �s idea but I think my students would find it a little difficult to start with.
Do you have picture flashcards for the verbs you want to introduce?
If you do I would start with a karuta game - you put the cards in the center face up and say one in the simple past i.e. washed my face. The students have to try to get the right card. As they already know the present tense it �s quite easy for them and they should be able to do it without much difficulty. When they get the card say the language again and ask them what is different to what they have already learned. Repeat if for them if necessary. When they guess tell them that �s how you put an English verb in the past (regular verbs) and get them to say it 3 times to a rhythm. Repeat till all cards are done, adding "I" and "yesterday" etc. halfway through the game if the students are up to it.
Play another game to consolidate. How about muscial cards. Put cards in a big circle. Play music. Students walk round while music is on and stop at nearest card when music stops. Each present your card and turn over. Continue till all cards are finished.
Then you can int. negative. Maye do by talking about your Sunday with positive and negative sents. Again try to get students to guess meaning. When they do drill a few cards in the negative, then do a game to consolidate it. How about the guess the card game? Split the class into 2 teams. One team chooses a card they "did" yesterday and tells you. The other team guesses "You... yesterday" (revising affirmative), they answer "No, we didn �t... yesterday" or "Yes, we ...ed yesterday" as appropriate. Then reverse roles.
If you still have more time put the cards in a circle and play a dice and counter game. Sts make truthful (affirmative or negative) sentences about the card they land on.
Then go into Saludos �s game - then the other students will feel confident using the negative as well so they can guess "You didn �t ... yesterday."
Not sure if this is the kind of thing you wanted but hope it gives you some ideas anyway.
Enjoy the class and the rest of your week.
Julia