Orbit pumpkins

[Spireite]

This year I planted 6 orbit pumpkin plants for the children to have something at Hallowe'en...the first 2 plants in the ground were great, pollinated straight away, are growing shrub like and now the fruits are just smaller than a jacko'lantern and beginning to turn orange.  The other 4 plants have all now finally set a fruit each, all different sizes...but now beginning to grow.  It seems to me that there seems to be no more female flowers  coming on the strongest 2 plants, as their fruit has been set for a while. 

Do these plants only ever produce one fruit each?  If I harvest the 2 oldest/largest will these plants then start to produce female flowers again and I might get a second fruit off each plant. 
Is there time to grow another fruit on each plant from scratch?
..and if I harvest them now will they store OK to last until October?

[Spireite]

[Jayb]

I've not grown the pumpkin variety Orbit, but as it's a F1 I think one fruit sounds a bit stingy? It's been a bit of a funny season here for squash so far and they have only really got down to business in the last couple of weeks. I've two large pumpkin growing and both are trying to set multiple fruits.

I think I read it was a semi bush type, are the plants still all growing strongly?