Thanks for your message. Here is a link to review on travel adaptors which should hopefully provide some helpful information: https://www.electricalsafetyfirst.org.uk/guidance/advice-for-you/when-travelling/travel-adaptor-for-costa-rica/ 

In relation to mosquitoes, due to the nature of the tour, it is worth taking repellent with you and nets shouldn't be relied upon with being provided in all hotels so we would recommend taking one with you.

We hope you have a wonderful time.

Best wishes,

Just You Team