I agree that finishing up with a orbital is a good way to go, but starting with a pad sander will save a lot of hours. It will not leave as many orbital swirls as a Rotex at low grit, so you can go over everything lightly with 120 and be ready for stain. Softwood decks need at least 120 to give a good appearance. 10 hours on 700 sqft is optimistic in my estimation. Anyways the railing will most likely take twice that long so you will have plenty of time on the knees. Having spent weeks of my life refinishing decks I am all about finding ways to make it easier.
Scott, you are talking about DEK when referring to Sikkens right? DEK is not recommended by Sikkens for refinishing as boards need to be encapsulated (finished 6 sides) before installation, and is not recommended for deck floors anyways by most due to its slipperiness. Sikkens SRD is a penetrating oil similar to Penofin or Messmers, but higher in solids. It is harder to apply, but gives a longer lasting coating and does not need to be stripped. It's all about prep in my experience.
Sikkens DEK on Cedar handrails is hard to beat short of an Epoxy coating. As long as it is maintained and was properly installed it will look like new for years. Here in Colorado at 8k feet the sun is the biggest enemy, so you need to protect thin wood from drying or it splinters and splits. DEK does that amazingly well, where penetrating oils on balusters will burn off and leave the surface hungry in a matter of months.