Well IMO, since you already said you would go to this one, I'd go and use it as a gauge for future decisions on these types of invitations. You can make it clear to him ahead of time that as far as you are concerned, having dinner together with your D should not be misconstrued to mean that you are ready to reconcile with him.
If your H reacts to them as just an opportunity to eat dinner together with no expectations, then I'd say go occasionally but not necessarily say yes to every single request. On the otherhand if your H looks at them as an indication that you are on the road to getting back together again or uses them to control you then they are probably not a good idea. Again this is just my opinion. Hope it helps.
