The Venice apartment in this trip report (traveling with parents) might work for you. Three bedrooms.

http://www.fodors.com/community/europe/loveners-2012-great-italian-caper.cfm

Popolo Borghese is better located. The grey is too far out.

Capo Africa apartment is really not close to anything except the Colosseum. If you stay at Capo, I would make use of the little electric bus (117)that runs through the historic center.
http://www.atac.roma.it/files/doc.asp?r=9

If you state your budget, you will get other apartment suggestions.

Thanks for the respose kybourbon. Will definitely check the apartment that report.

Budget : 150-180 Euros per day

Five adults and a five year old, in 2-BR, 2-bath? I'd definitely look for accommodation with some nice living space. We were in Rome, over Thanksgiving, with 2 couples, a single, and a toddler: this is an wonderful location: http://www.residenzagiubbonari.com/

Thanks just27...will try this one too.

Any feedback on the apartment I have chosen in Venice....especially location please?

Your apartment in Venice doesn't have an ideal layout for your party of 6. I would definitely look for a three bedroom. Is your budget of 150-180 Euro per person, per couple, per room, per night for everyone? It may be a little low if it is per night for everyone. Can't exactly pinpoint the location from the information available.

Thanks mamcalice....space we will adjust I guess ( we live in such houses in Bombay ....the budget is per night for all....could go up a little!
Need feedback on the location esp.

And need help for choice in Rome......we always go through sleepinitaly....but since I am super late in planning this time....don't see many available. Any options?

Thanks again

I don't know the specific apartment in Venice, but the Canareggio is a little out of the way (even though Venice is small and walkable from most places).

Just as another possibility, I recommend contacting venicerentals.com. Tell them what you're looking for, including a central location, and see what they come up with. I do think your budget is a little low for 6 people, but see what venice rentals has to offer.

Thanks downtownbrown! Any suggestions for Rome?

60 isn't elderly unless there are health issues.

Venice is all walking all the time except when on a,vaporetto, and that is all crowds all the time. Absolutely Worth it, just don'!t overplan!