Our school also does a year end picnic on the last day of school. We do not charge for this. It's part of our budget for the year. The teachers have games organized for the kids all day. The PTO provides hot dogs, chips, and watermelon. We also have a candy toss for the big kids and a separate one for any smaller siblings that might be there. Everyone seems to have a good time.
We did an end of the year picnic. We served hot dogs and dilly bars from Dairy Queen. We only only charged a small amount with the PTo taking a hit in the end. It was a lot of fun. No activities were organized. The children just played on the playground equipment. I think they just enjoyed the free time with all of their friends.
Part of the answer might be dependent on if it also needs to be a fundraiser, just break even, or even if the PTO plans to underwrite it.
One of the easiest things I can think of is a family skate night (or miniature golf or whatever.) Businesses like that generally love to set up nights for groups - and usually even give you part of the proceeds.
Our Spring event (early May) will be a family night at the school with pizza and games (probabably bingo) in the cafeteria, a silent auction in the foyer, and a sockhop in the gym. (We are K-5.) It will take some volunteers, but not as many as a Carnival. We are doing it in conjunction with our spring Book Fair, so the library will also be open for Book Fair sales.
You could do any or all of the pieces, not necessarily the whole thing.
We are interested in providing an event for both kids and parents to take place at the end of the school year. Hopefully, something that does not require a lot of work easy to organize. As we do a Spring Carnival in March. Any ideas would be greatly appreciated. Thanks