Well you are quite lucky compared with all the people who have been asking what to do about theirs that have all but disappeared this summer! You could try cutting off the long growths and they will probably branch out again from lower down. A trip to your garden centre will give you a choice of what to replace them with if that doesn't work, but you won't find a big choice of bedding plants at this time of year - its a case of looking to see what there is. Pelargoniums would be fine, but you would pay quite a lot for mature plants.