hi,
I think apart from organizing various initiatives, you must speak to the senior concerned. You don't need to play a blame-game there. Just let him know politely that you had got some informal feedback from some of the employees that they feel too pushed sometimes. Perhaps, he could adopt a strategy of allowing the team members to use their own approach to achieve targets - it doesn't matter how and when they work as long as they can produce targets. Try to convince him by saying that you can use this approach on a trial basis for a month and would closely monitor the results as HR.
Apart from that, i think its very important to have a conducive environment to work. So if your boss feels that taking the employees out might be a waste of time, do something within the premises. Small things like a 'surprise bash for stars' (stars here are the employees of the company) with nothing much but some small snacks and cold drinks, could be a good idea.
Other initiatives include Appreciation cards (to be given to employees amongst them or from a senior to a team member) if he thinks the employee has done something really worthwhile and beyond his scope of work. You can put up a public display board and pin up these cards so that the others can also see and read the comments and get inspired.
Other incentives are on the spot cash / voucher awards - just get all the seniors in your company together and decide on one person who gets that award - you can do this quarterly/monthly,depending upon the budget that gets approved.
I hope my tips help you out. All the best !
Regards