If your rates include Breakfast at the SL then that will save you a LOT of money over the Oriental. For 6 breakfasts I would estimate $150 plus tax + service per day at The Oriental.

The Krungthep wing is very very nice at the Shangri La and is in a separate wing to the main hotel, it feels very much like a boutique hotel, All rooms include a very nice balcony overlooking the river.

The Krungthep wing is also excellently situated for the sky train.

I think you may also fine that because the Shangri La has a slightly more relaxed atmosphere it might be more suuited to a family of 6 that includes 4 children.

Either way, both are world class hotels and any critiscism levelled at either is usually minor.