Thanks for the replies!

We're arriving in San Francisco on 25th September and are staying until Sunday 29th. The Oracle conference is on until the 26th so rates are expensive for the first two nights (SF $650, $441 and MH $639, $394) and we would have to book a two night minimum if we were paying for those nights. So we have decided to use points for these as I can still book them on the old rate and I have enough for either properties.

For the following 2 nights, the best rates are on F&F (SF standard king bed $351, $260 or MH Club $278, $278).

I let my Ambassador status lapse last year so the other option is to buy back in and use the bogof on the Friday - best flex rate for the Friday is SF $389 and MH $229 for standard rooms. The best flex club rate for the MH isn't bad but I'm not sure that would be offered on the Ambassador cert rate?