I really like chatuchak so would say yes definitely go. One tip go early ( be there by 9.30am) it gets REALLY hot and crowded later in the day. Also get a nancy chandlers map which has a section on the market and check out the cool Viva bars ( one is in section 28) fab little pit stops) I also like the luxe city guide to Bangkok which has a fantastic section on Chatuchak.
Aside from that there are tons of things to do in BKK, have you been before?

I agree, Chatchuchak is best visited as early as possible to avoid the heat. we were there in Dec and started out on the BTS early so we arrived in time for breakfast at one of the noodle stalls near thge main entrance. As Smeagol recommends, get a copy of the NC map. Without it, it will be very difficult to find anything that interests you. Worth visting the outer edges of the market just to see some of the weirder stuff on offer.

Chinatown markets are in league of their own and well worth a few hours but that can be done any day of the week.

Thanks.

We actually haven't been before, so maybe I have no business soliciting additional places to see, but I thought I had seen a couple recommendations for things only open on certain days, so I thought I'd ask. Feel free to share your "must sees" for 2 days (but please try to refrain from reminding us it's not enough time).

Generally we were planning to see the "major" sites (Wat Arun, Wat Pho, Wat Phra Kaew, Grand Palace) plus maybe a tour that included the khlongs, possibly a floating market, the Chinatown food tour...

Of course we also need to be realistic/flexible as to how much time we have, especially as it's the beginning of our trip so we want to allow for jet lag/climate adjustment.

To be honest, I think what you have planned above and chatuchak will be all you will fit in, but it will be a great 2 days.
Where are you staying? I would suggest by the river as its more convenient for the major tourist sites in BKK and great area for a first time visitor. ( staying in town is fab too but for wht you want to see I think the river area may be best)
PS and of course this is the right place to solicit additional places suggestions

Sounds like an excellent plan to me. I would just add in a visit to Wat Po massage school just outside the temple complex (amazing how it revives you during a hard days sightseeing!). Easy enough to incorporate all of the places you suggest by just getting the BTS to Saphin Taskin and getting on the public boat which has stops at each place (you will need to get a cross river boat for wat arun).

PS It would be a good idea to sort out some places to eat in advance as the choice in BKK is vast.

But whatever you do don't fall of the scam that the palace/Wat Po are closed and then get invited to to go visit a gem store because it's the Buddhas/ kings birthday and are having a massive sale in their honour!

Do the Calypso Cabaret- great Ladyboy show. Skip the dinner option. Its located at the Asia Hotel -access directly from the skytrain. Classy show good for all ages. Bring your camera, also get photos of the "girls" with you after the show - but do tip them (about 40 baht). You can purchase your tickets on their website and pick your seats.Then just pick up your tickets at their box office at the Asia Hotel on the day of the show.. One free drink with the late show (as I recall it starts about 8 pm). You will have a great time!
Do not ride a TUK TUK and in the taxis make sure they use the meter before you get in, otherwise get another cab. If Thai people approach you on the street more often than not its another scam- just ignore them.

Thanks. We are planning to stay by the river (got a discount rate at the Peninsula and decided to go for it because the trip is a celebration). Have heard from a couple people of the "palace is closed" scam.

We're not huge shoppers, but if ever there was a place to do some, Bangkok sounds like it might be it.

Appreciate the tip about considering places to eat in advance.