I've been at Easter several times and never been disappointed. Saying that, the visits when Easter has fallen later in April were slightly better. As Rob says, it's into April before the Eleonoras start to arrive, but there are plenty of other migrants.
I've stayed in Puerto Pollensa each time I've been.
The Boquer usually holds Balearic (Marmora's) warbler, Blue Rock Thrush, booted eagle and possibly Black Vulture (but the moutains are the best bet) also migrating Egyptian vulture and black kite. I've had migrating Rock Thrush on a couple of occasions in front of the Boquer farm. Black-eared wheatear is another possibilty, hoopoe, woodchat shrike, crag martin, wryneck etc.
Bee-eaters should be arriving and Scops owls will be calling.
Audouin's gulls are common along the bay.
S'Albufera should be alive. Great reed warblers and nightingales should be in, cetti's warblers and fan-tailed warblers everywhere and a chance of moustached warbler on the long track running south at the bridge on the way to the visitors' centre.
Red crested pochards in theii hundreds, with a small number of white-headed ducks (I've also seen 3 marbled duck on one visit). Purple gallinules everywhere and there are some crested coots from a release scheme, recognisable by their white plastic collars.
Whiskered terns and gull-billed terns are a possbility.
Raptors - osprey and marsh harrier are bankers.
All the herons/egrets are possible including great white egret. I've heard (but unfortunately didn't see) a booming bittern at S'Albuferetta. The breeding/roosting area at the entrance to S'Albufera usually holds a few squacco herons and night herons amongst the flocks of little and cattle egrets.
Waders include stone curlew, glossy ibis, spotted redshank, little stint, greenshank, black-winged stilt, kentish & little-ringed plovers, etc, etc (but high water levels could reduced wader numbers).
The list is by no means complete. I've not been since 2004, but just writing this makes it seem like yesterday.
If you can get along the Formentor peninsula there's a chance of Cory's and balearic shearwaters.
The bus service is good from Puerto Pollensa to S'Albufera, but if you've got a car then it's worth a trip down to the southern tip of the island and a bit of sea-watching from the point there, combined with a scan of the salt-pans in the nearby salinas.