Trees would be a poor choice, far too heavy, far too little oxygen, too much water needed. A football pitch filled with trees would only give enough oxygen for 50 people at peak output, and only supply oxygen for half the time assuming perfect conditions. This is also assuming they are near to or fully grown.
By the time you have taken into account the tree's full respiratory pattern (they take in oxygen when they are not photosynthesizing) a football pitch full of trees would be lucky to supply a handful of people (5 to 8) with oxygen and if these people were active (10k steps a day) that number would drop further.
The need for redundancy would also be high. In an artificial environment like this, a 10% to 15% loss of trees would be common place and could happen quickly and result in losing the oxygen for 1 person. I would suggest a safety factor of 10 to 1 for which we, depending on the efficiency, would need 1.5 to 2 football pitches of trees each.
To give you an idea the oxygen the Amazon rain forest produces only supplies oxygen to the life that lives within it; next to no oxygen from the Amazon benefits the rest of the world.
However, all is not lost. Most of the oxygen on earth comes from plant life in the oceans, namely phytoplankton. Now comes the good bit...
Imagine a large skylight above your grow area which is double glazed. Instead of being empty it is filled with water and phytoplankton. This mix is continuously circulated and fed nutrients. The first bonus: a window the size of a football pitch has the potential to provide oxygen to 1000 people. And second: water has a good weight to radiation protect vaule.
Under the window I would have a farm stocked with fast growing, green stem, edible plants. Fast means more oxygen green stem will photosynthesize as well as the leaves. A football pitch sized farm could supply 750 to 1000 people with food at full efficiency and a little help from science (being developed at the moment).
If set up correctly, the phytoplankton would meet the oxygen needs of the population and the farm below would supply the safety margin. Once enough oxygen has been stored as a back up supply, the ongoing excess would be used for rocket fuel etc.
The estimates above come from projects based here on the planet's surface. We can recreate most of the needs for plants in space. Two things we don't have an easy or clear answer to though: how will the lack of gravity and the exposure to radiation affect the amount of oxygen produced and the quality of the food for consumption?