Hi Lisa,
My family stayed in Alvor last summer and we had a lovely holiday there. Funnily enough, we are returning this year on the same date as yourself for 2 weeks.
We rented a 2-bed private apartment on the Dunas Do Alvor complex (which is next door to Vila Da Praia) and really liked it...good location, nice pool and a number of reasonably-priced bars and places to eat onsite and nearby, as well as a small supermarket on site which was handy. I believe Thomsons also have some rooms there but I think the private ones are furnished to a better standard....ours was a real home from home with all mod cons provided. We had a look at an apartment at the Vila Da Praia next door and that's also a lovely secure complex with a nice pool area, albeit there didn't seem to be any onsite facilities if that's important. Not aware of any gym facilities at either of these though , but i think there's one at one of the large Pestana hotels closeby. Alternatively, if your other half likes running, I enjoyed a few long morning runs along the beach and dune area, which stretch for miles.
Alvor itself is magical. It's quite rustic in a way, but has a lovely feel to it, particularly at night, with some fab places to dine in or just enjoy a quiet drink by the sea. My kids are 6 and 3 and we felt so safe and at home there.
If you need any more info, i'm more than happy to help if i can.
Thanks
Mark