We've done cinema parties a couple of times. It is really tricky to know what films are on and when, as the multiplexes don't release film times until the THursday of the preceding week ime.
What we did was to issue invites, stating day and approx timescale, confirming exact details once the cinema had publicised its timings.
This may be a bit tricky if you want to book a restaurant table as well...you may need a backup plan for something to do to kill half an hour between film and eating or vice versa, though often the large multiplexes have multiple screenings of new releases.
Going to see the kids special would be less of a headache, as you will know in advance what time it is (an will prob be cheaper too) but just won't be a new film. Maybe you could go to that, and take your DSto see the film he wants as an added treat.
I think asking parents to take to the cinema is fine...you could offer to let parents know who else is going so they can share lifts?