Great! You'll love it. To eat in Obidos old town is easy peasy it's a small place packed with choices. Follow your nose, there really isn't a bad place unless you are very unlucky. If you don't mind a short ride then head to Foz do Arelho. 10 mins max. On the road into the village there is a restaurant called tibinos on your right. This gets busy on a weekend so service will be slower than usual and you my need to book.
FB page
https://www.facebook.com/Tibino.petisco/ closed on a Tuesday.
But luckily right next door is another great restaurant called Tavola. I think this does the best fish in the area and has other typical Portuguese dishes.
Before dinner or after, you could head to the beach, continue past these restaurants through the village straight over a round about past the camper van site where you will see a turning on your left. Go along there (looks a bit like just parking on the beach at first) and you will see a few cafes and restaurants. (most are good for eating also). Towards the end of these is a place called Coco's. Best gin and tonics in town and a great place to watch the sun go down.
http://cocosbeachclub.pt/bem-vindos/
It's a great area, and prices are very good.
Have a great time and let us know how you liked it... or not