We went to tenerife in january, it was our first holiday without the dcs. It wasnt an adults only hotel, but had no facilities for chikdren, so there were only two there and they were very well behaved and oarents were very mindful of other guests. We paid 1k all inclusive for a week and it was amazing
All inclusive makes holidays very affordable at the moment - the exchange rate is so poor. A friend of mine went to Majorca all inclusive recently and upon talking to other people at their hotel that stayed bed and breakfast, they only paid £125 more per person. I think you's struggle to have 7 evening meals, the odd lunch and all your drinks for £250 per couple.
I understand what you mean about the freedom to wander and choose your restaurant, but some all inclusives don't have just the one restaurant - several we have stayed in have had the main buffet restaurant and 2 or 3 'speciality' restaurants.
there is a website called awaywithoutthekids.com they might be a good place to start. sorry can't be more help we don't have the option to go away without ours so even a walk up the driveway together seems good to me!whatever you choose i am sure you will have fun.