Mark - I assume OP has altitude points - which convert to a few programs at 2:1.
I don’t know which carriers you might find to get to Orlando, sorry. It might be a hard place to get to with one carrier, and may require a change at LAX?
To get to New York , for example, on Singapore you would need 182,750 Krisflyer + $1250 per person return in business. So for four of you need 731,000 Krisflyer (which would require 1,462,000 Altitude points) plus $5,000 in taxes.
For economy, same flights its 93,500 points and $1,186 each - so 374,000 Krisflyer (748,000 Altitudes) and $4,744.
You can see why business class redemptions offer better value!
I don’t think you will have much luck getting four seats together, can you split your party into two groups of two travelling one or two days apart? You would also need to book at the end of this year (11-12 months before flights) to get spots, but I think your biggest issue would be to work out how to get to Orlando…my guess is most carriers servicing Melbourne would only service key cities in the US (LA and NY) but I am only really familiar with Singapore, you might have more luck on Cathay, Malaysian or the middle eastern carriers.