Northern Ireland Fanzone at THE STOKERS HALT #gawa
Northern Ireland vs Estonia 7.45pm KO Thursday
Nothern Ireland vs Belarus 6.00pm KO Sunday
Northern Ireland face Estonia at Windsor Park on Thursday and host Belarus at the same venue on Sunday, with the Netherlands and Germany the other teams in their group.
O'Neill must already plan without midfielder Oliver Norwood, who opted out of the squad for the opening Group C qualifying games for "personal reasons".
The NI boss has expressed concerns over the lack of first-team action enjoyed by many of his squad in recent months but skipper Steven Davis played a full 90 minutes for Rangers at the weekend.
Grigg was on target in Sunderland's 2-1 League One win over Walsall, Liam Boyce found the net after being recalled to the Burton Albion starting line-up and Niall McGinn was on target in Aberdeen's 1-1 draw with Livingston.
"There's a great spirit in the group but we know the challenge that lies ahead in terms of the quality of the teams we have to play," said O'Neill.
"We need to build momentum so we will go and attack and try to win the games. We have plenty of attacking options.
"We need to play with the same intensity as we have in recent years and look for the same level of performance.