Mo's is a kitschy family-friendly seafood chain. Great ocean front location in Tolovana, just South of the bustle in Cannon Beach proper. Walk up from the beach. Plenty of parking, too. Be prepared for the gift shop at the entry, in case your little ones are prone to "need" something.
The Food: Let's face it, you aren't going to Mo's for an amazing culinary experience. The crab melt is average at best (so much mayo). The chowder is ok. Skip the crab cakes. The salads are massive. There is a broad menu. Remember this is Oregon, so the cheese in anything is usually Tillmook cheddar (yum). In the end, Mo's food is nothing special and priced just slightly too high for the quality. One in our party just shrugged and said meh.
The Restaurant: The service is efficient. The view is fabulous. It is very busy - and they pack 'em in. There is a lot of ambient noise (the neighboring tables are right at your elbows).
When we next travel the OR coast with family, we will not stop at Mo's - the nostalgia is no longer enough to make us return. If you are travelling with young people, then this might be a good fit. If your group is only adults, then skip it for better fare in town.