The "seedy" issue on Le Meridien is not really a big deal unless you are the most puritanical people in the world. In which case Thailand may not be the place for you. There are plenty of "respectable" businesses in the neighborhood. You will walk past many places offering massage and most of them are legit. If you want to avoid the gogo bars that is easily done as those places are on sidestreets.
It's a relatively short walk to the BTS and subway which makes getting to some places like shopping easy. But for most of the big tourist sites you will need a cab or car from Le Meridien's location. Since there are 4 of you it is possible to get a tour guide and driver with a van to take you around for a reasonable price.
I just spent a couple of nights there last week. I liked it fine. It's very "designed" and trying to be boutique-y which I guess is what LM was going for. The breakfast buffet is pretty good. Internet connection is very pricey. But if you are staying free anyway that may not be a big deal. Or if somehow you can live without the net. :-) I stayed in the basic room which was smallish. But if you are getting upgrades you should be in a larger room.