I wouldn't say that Wales feels 'shut' at Easter. There is plenty to do. Fantastic beaches, fantastic views, fantastic cycle tracks, mountains to climb, some beautiful self catering cottages,holiday parks, lovely hotels, shops, restaurants...I love it !
we stay at wringworthy holiday cottages near Looe. easiest part of cornwall to get to as you go down the a38 not the a30. their newsletter has pics of kids rolling eggs etc so assume they offer this at easter. their website says they take dogs. Wales can feel a bit "shut" at Easter seems to get going mainly at May half term. if you do fancy wales then we stay near Portmadoc. nice long walks, portmeirion, tree surfing, castles. have a look at some of the pet websites like petswelcome or dogfriendly as it is finding somewhere that takes dogs thats the issue.
We are looking for accommodation for 2 adults, 2 children and a small non-moulting dog for the first week of April (after Easter weekend). Thinking Snowdon but anywhere within a 3 hour drive of Bristol really. Nice walks and a local pub that serves food essential.