Equipment, fills
In Kingston check with TomR's Northern Tech Diving
Going east, you just have to visit the local "toy store" Dive Tech in Mallorytown. Dan can help you out with fills, equipment.
shore stuff
In Kingston, the gang there will have to help you out, but check out NTD's web for their great info page on shore diving.
Brockville has a couple, but on the weekend they're likely to be packed with OW classes.
Prescott - The Rothsay, a wreck near shore, with a good rope course heading to it. There is also the "water park" in town, but as in Brockville, this is likely to be packed with OW classes.
Cardinal (1) Connestoga - a wreck easy to get to as you can see the smoke stack from shore! (2) Lock 28. This is great if you can hook up with an other set of divers, then arrange to have one vehicle at Lock 28 and one at the Connestoga. Great drift/wreck dive.
charters
As the Kingston gang are having the mooring project on the 3rd weekend of May, the charters should be in full swing by then. Check with Divedude (BigJim Charters) and TomR (Northern Tech Divers) both on here on SB, they run charters and should be able to help you out
Many of the charters in the Brockville area are putting their boats in in the first week of May. I'll PM some numbers in a bit, but check out BottomTimes (Evan is great), and Above&Below (don't tell Jymi I sent you hehehe)
Accommodation
So many hotels & motels with very reasonable rates. Many in the Brockville area offer discounts to divers. I do know of a couple of B&Bs, one is very friendly to divers (since the owner is one!) again that'll be in the PM.
Sorry I'm going to miss your visit, but come on up, have a great time then think of joining the freaks in the Kingston gathering at the end of August!