use common knowlegde they both have to be ran seperate with either a zone valve or seperate pumps. then its nice to use a taco zone control board. alsorun your water heater off the boiler. ( need a water heater for this spacific application) also make sure your boiler is big enough for the job.

Our previous home had original radiators in every room except the living room in which another PO had installed baseboard radiators. I have no idea why since, to get the same heat output as a stand-up radiator, you need lots and lots of lineal feet of baseboard radiator. Anyway, for the most part we just ignored them and put furniture where we wanted. You can see in the picture (please ignore how bland the room is!). We painted them to match the walls (they were originally maroon and the walls were muddy mauve, but that's another story!) The bookcases and TV stand are right up against the heaters. We did have furniture on feet so they weren't completely blocked. And the sofa is pulled about a foot away from the windows and that run of the heater. Hot water baseboards don't get hot enough to be a fire hazard, but electric ones do. Never put anything directly up against an electric baseboard heater.

What kind of radiators do you currently have, aluminum fin convectors or cast iron radiators? What kind of boiler do you have, old-school 80% or a condensing boiler? If he former, is a condensing boiler in your future? I think that in-floor radiant is the way to go if the boiler will support the added load. I'd want it for happy feet as klem1 pointed out. You may need a mixing valve to reduce the temperature of the water to the floor heat. For wood floors they are used. With tile, you might not need them. I really don't know. Keep in mind that high mass (as in concrete slab) radiant is not very responsive so set-backs do not work that well. With a condensing boiler, you might not be using set-backs anyway. You can also install hydronic towel bar heaters. Toe-kick heaters are also an option, but they are not exactly silent. These, however, need to be combined with radiant floor heat by someone that knows what they are doing. You need water temp on the order of aluminum fin convectors or higher for toe kick heaters to be effective and temperature and the same thing goes for the towel bar heaters. You might want to do ROI calculations after getting quotes to install in-floor radiant electric vs. hydronic. Whatever the challenges, in floor radiant is what I'd strive for. It is doable by someone that has the right (hydronic) stuff. One other opinion, insulate the crap out of it and you won't need much heat. There is a good ROI for insulation in NE PA. I grew up just North of Binghamton and I spent time in PGH and Philly so I know your climate well.

I recently put 1"x4" PVC trim board in for someone as garage baseboard, the same kind of stuff people use to trim out garage openings so it doesn't rot. It runs about $8-10 per 8 foot piece on contractor pricing in my area, so not super cheap but not insane. PVC will of course never rot, you can paint it, and it will seal very well to the slab if you don't want water running under there if you use a tri-polymer caulk. PVC will also not be capable of wicking any moisture up to your sheet rock, as even though treated lumber may not rot, it can still take water up and ruin your drywall.