yes, you could do a big box of chocolates - they get loads and will pick a box each the teachers don't expect you to do a present each - they know it's too expensive!
it's ok to give one present to your child's key worker only
or do both
you could also decorate a dozen cupcakes/muffins together with DS and take that in on last day - teachers can pick one each, sweet, easy, personal, cheap, doesn't gather dust and DS will be brimming with pride! perfect
give cards also to each if you want, but I just do one big one for each and one for key worker, again preferably homemade cards, so much fun!