Noboribetsu

Good day to everyone.
Need advise on below as i will be staying in hakodate & sapporo for my 6 nights 7 days trip in hokkaido this coming May.
1) Travel to Noboribetsu from sapporo is better or from hakodate?
2) Is it possible to complete Lake Toya & Noboribetsu in one day?
3) shall i appoint local tour guide / transport as we are in a 9 adults & 1 child group? Or can i go by train? Would it be too tiring if i travel by train
TQVM in advance.

Travel to Noboribetsu from sapporo is better or from hakodate?

From Sapporo is "better". Not only is it much closer, but you also have more options, as explained here:
http://www.japan-guide.com/e/e6753.html

2) Is it possible to complete Lake Toya & Noboribetsu in one day?

It depends on what you mean with "complete". How many and which sights do you want to see? How many baths do you want to take? It also depends on your means on transport. A rental car will allow you to see 2-3 time more places. Last but not least, onsen resorts are generally best enjoyed with an overnight stay. So, I personally would not be able to "complete" any of them on a single calendar day.

3) shall i appoint local tour guide / transport as we are in a 9 adults & 1 child group? Or can i go by train? Would it be too tiring if i travel by train

A car would help tremendously. Trains are not tiring, but they only get you as far as the railway stations. From there, you would have to take buses. And some places have very bad bus service, such as Showashinzan.

Thanks Uji