Jack-be-little grow more like an ornamental gourd than a pumpkin with the respect to the number of fruit you will get. If they have turned a deep orange like a pumpkin then there is a good chance they are done. I wouldn't pick them unless they have spent at least a month growing on the vine.

Personally I wouldn't remove the Jack-be-little plant simply because they are so productive. The other pumpkins you have just aren't near as productive. You might only get one or two pumpkins on each vine from the Sugar Pie and Howden plants. If your Jack-be-little plant is too big you could try pruning the vines. You can just pinch the tips on the vines and they will stop getting longer, but they will branch out and you would have to cut those back as they grow too.

Oh and you can eat Jack-be-littles, they are the perfect size to stuff.