How important are fireworks to you?
Most people are able to do more on a short party day then they are on a longer non-party day. Many people without party tickets avoid the party days with the parks closing at 6, and many people with party tickets use that as their only ticket for the day and don’t go into the parks till 4. So if you’re a ride-oriented group, a party day can be a great way to get everything in with minimal waits!
The downside, however, is that you won’t get to see the fireworks from within the park. Happily Ever After isn’t shown at all on party days. So if fireworks are important to you, that could make the decision.
You also might want to consider buying a Halloween party ticket yourself. They’re a TON of fun, and a personal favorite of mine. There’s a special parade, special fireworks, special shows, short lines for rides, trick-or-treating, and, new to this year, there will be special overlays on a few rides! It’s also the only opportunity for adults to wear a costume in Disney Parks. I went as a jungle cruise skipper last year and got a ton of attention for it-from the jungle cruise cast members and also just random other guests. However, I do realize party tickets can be quite expensive and that might not be within the plan.
Assuming you don’t have an interest in a party ticket, I would go on a party day. I’d make a dinner reservation at a monorail resort restaurant, and then watch the special fireworks from the beach at the Poly (or from the restaurant, depending on where you eat). I once got sticky wings from Kona Cafe to go and ate them on the beach watching the fireworks - I’d totally recommend this as it was fabulous!
If you did end up looking into a party ticket, you could even make it a two day trip! You can get in to magic kingdom at 4 with a party ticket, so plan on being at the gates just about 15 minutes before that. The party goes till midnight. Then, you could use your one day ticket either the day before or after the party. You could either go to a different park and have the party qualify as your magic kingdom day (I’d personally advocate Animal Kingdom as a great mix of rides, shows, and activities), or you could go back to magic kingdom with a no-stress mentality. You’d have done most of the rides with shorter lines, so you could just revisit favorites and stake out a spot to watch happily ever after.
