Hi, I'll try to help as much as I can. I believe on the trade in program they'll give you 50% of the current retail price/value toward a new bag of equal or greater value, so you can pick anything and then just pay the difference. I'm not sure what happens if you pick a bag that is less expensive because I don't think you are allowed to buy more than one item to come up with the total, but I'm not sure. I've never actually done it.
Regarding the bags you mentioned, I looked them up on QVC. I believe all of them will slouch a little as they soften to create a little bit more of a strap drop, so this isn't always that accurate. However the croco fino is a more structured bag so it might not soften too much.
Kingston Hobo: Measures approximately 14-1/4"W x 9-1/2"H x 6"D with a 7" to 10" strap drop; weighs approximately 2 lbs, 10 oz
Croco Fino Hobo: Measures approximately 13"W x 8-1/2"H x 5-3/4"D with a 6-1/2" to 8-1/2" strap drop; weighs approximately 1 lb, 8 oz
Double Pocket Satchel: Measures approximately 14-1/2"W x 11"H x 6"D with 3" handles and an 8" to 10" strap drop; weighs approximately 3 lbs, 4 oz
Here are some other suggestions: Do you like the Toledo leather? There is a nice hobo style which is relative lighter in weight which might be an option for you if you like lighter bags. Also, the Calf leather bags are lighter in weight. There is a hobo with a longer strap drop and it's light in weight. I just received my calf convertible satchel and the strap is long, but it has a piece that comes off to create a shorter shoulder bag. It's a lighter weight and has an outside zipper pocket which I love. I believe any of the satchels with the longer straps can be doubled and reattached to create a should bag look. Also, if you really love a bag, but don't like the long strap you can take it to a shoe shop and they can shorten the strap for you. I believe I heard from a friend on youtube that it costs around $10. She's done it on some of her Dooney's.
Good luck. I hope you find one that you love and works for you. Let us know what you chose.