Everybody/everyone is is correct because although you are talking about a group of people, it has been made into one singular group.
- Everybody is happy that we are going to Spain next year.
- Everyone is welcome in our house.
Recommended for you:
WAS WERE Usage With Examples
How to use the following words – IS, WAS, THAT, THE …
BE, BEEN and BEING Usage in English
Everybody – Everyone – Somebody – Someone