You are playing our favorite convention xyz, in the flavor that 2♣ (forcing 2♦ from partner) followed by 2♥ would be a mild invite, while followed by 3♥ would be a strong invite. 2♦ is a general game force, and if you follow that up with a 3♥ rebid, your partner will understand that as 6 hearts but doubts about the strain.
(Sorry, 2NT is not available for invites.)
What is your plan?
Arend
Edit: 1NT is 12-14

Help

Opponents all silent, your partner opens in 2. position and the bidding goes
1♦-1♥-1NT