Does anyone have an updated version of classic 60's desserts that would be great for a picnic?

Apple and cherry pies always a picnic item at my family picnics!(any fruit pie that can sit out for a while)

Here's another '60s classic salad: stained glass salad, complete with Jello, Dream Whip, and a graham cracker crust:

https://clickamericana.com/topics/food-drink/jell-o-crown-jewel-window-glass-dessert-recipes-1960s

Here's a recipe for a lime Jello 'salad'. This is a great example of the odd way salads were interpreted in the 1950s and 1960s--slap a leaf of iceberg lettuce on a plate, toss something sweet on top, add a blob of mayonnaise, and call it a salad. Minus the lettuce leaf and the mayonnaise, this would be a decent dessert.

https://magnoliadays.com/creamy-lime-gelatin-salad/

Here's a recipe for a lime Jello 'salad'. This is a great example of the odd way salads were interpreted in the 1950s and 1960s--slap a leaf of iceberg lettuce on a plate, toss something sweet on top, add a blob of mayonnaise, and call it a salad. Minus the lettuce leaf and the mayonnaise, this would be a decent dessert.

https://magnoliadays.com/creamy-lime-gelatin-salad/

Anything with Jell-O. My family still brings this strawberry-Jell-O-pretzel-Cool-Whip thingy to picnics. Google it. It's actually really good.

Angels' food cake, updated with roasted sugar (the link for the cake recipe is at the bottom of the article about roasting sugar): https://food52.com/blog/20235-how-to-make-and-use-roasted-sugar

Pineapple upside down cake isn't bad in its 60's incarnation, but using fresh pineapple instead of canned would definitely be a step up. Here's a recipe from Flour Bakery in Boston -- they are particularly good at this sort of homey American dessert: https://food52.com/recipes/16419-flour-bakery-s-pineapple-upside-down-cake

You had me until picnic.
Here's a list of some popular desserts...only you can tell if you have the equipment to present these on a picnic.
http://www.metv.com/lists/10-popular-desserts-of-the-1960s-that-deserve-a-comeback

A classic and picnic perfect, 7-Layer Bars. Do a search online and many versions pop up. Really easy to make and transport.

One option for you: https://food52.com/blog/20151-how-to-make-jello-with-fresh-fruit