Where to sit is a bit of a 'how long is a piece of string' type question, but as a veteran Virgin flier, I'll help you out as best I can.
As someone who usually travels solo or with other adults, I've always gone for emergency exit (EE) seats whenever possible. These give you the advantage of vastly more legroom, and the ability to just forward step out of your seat when necessary and not clamber over/force other people to get up. This goes for any plane of course, not just virgin, it's just more relevant/important for long haul flights such as to Orlando.
The problem with this for you is that kids cannot be seated in emergency exit seats. However, as I recall, certain EE seats on 747's are located along side the 4-wide middle seats on 747's. This could be a good option for you.
If you do want to go for EE seats, as these cannot be pre-booked, the only way to get them is to get to the airport extra early, I'd say at least 3 - 3.5 hours before take off time, to ensure you get first dibs by being first in the book-in queue. It might seem a pain, but believe me, it's worth it, especially if anyone in your party is tall, and airports now have plenty of stuff to entertain the rugrats !
I'm encountering this exact problem myself for the first time this Chrimbo as I'm going to Disney with my lady and her two boys 12 & 10, and using BA for the first time ever to fly to the USA (Big saving on flights and better dates available) so we'll be there even earlier than usual to get this sorted !
I'd also advise this might be a good idea as Virgin seem to be using the older 747's in it's fleet for the Orlando run these days, and if anything the room is that bit tighter.
If you dont want to go that way, then bulkhead seats are your next best alternative. Bulk head seats are all those facing one of the utility/crew areas in the passenger area of the plane. These usually give a little more than normal legroom, which could make the difference between comfort and being unable to walk other than like a wounded duck when you arrive in Disneyville !
As you're a party of five, you are going to have to have at least one person sitting across an aisle from the main group, even if you go for the middle set of 4 seats for the bulk of you. The advantage to that is you get 3 aisle seats, so some judicious rearranging mid-flight should enable everyone to keep their legs moving !
I cant give you specific seat numbers and locations, but this marvellous website can !!
http://www.seatmap.com
Believe it or not, if you enter the date, airline and number of your flight, this site can give you a plan of the plane you are flying on and show you what seats are booked/available, so you can actually choose the specific seats you want if need be !!
It seems to be very accurate - I called BA to book seats together as our flight is at a busy time and wanted to be sure we'd all be together in case the EE seat plan falls apart, and later in the day, when I checked on the plan for our flight, the seats we were allocated were now showing as taken when previously they had been available !
I hope this is a help to you. If you need any other advice/info, feel free to ask here or post me a private message !
