The poem is built around a joke that isn't quite a joke: a "committee for invention of play." Committees stand for routine and paperwork, while play is supposed to be free and spontaneous. Putting them together suggests a speaker who treats imagination as serious daily work, something done as "usual business," yet who still enjoys it. The work is "done with pleasure."
Then the poem turns. The pleasure is compared to "a dark night / that bled out," which is a strange and slightly unsettling image. A night bleeding out could mean darkness draining away into dawn, or something wounded slowly giving up its life. Judging by the imagery, the speaker may be suggesting that enjoyment and darkness can sit side by side, or that the work carries a quiet sense of loss or ending.
The mood is wry, dreamy, and a little eerie. It's light on the surface, but the last image leaves a shadow, and the poem doesn't explain which feeling should win.