Ideal time of year to visit?

Very touristy question coming up, so please bear with me:

My mom and I were thinking of coming to visit from America (Oregon) in either late March or early April. What is the weather usually like around that time of year?

I'm also a huge animal lover and would love to see the puffins, ponies, otters and their cute little babies as well. Would those months be good for animal watching too?