If you are hiring a car (or bringing one with you remember that TT practice week starts on that friday and the Island will start to fill up with literally thousands of motor cycles (interesting driving if you are not used to 'wrong' side of road).
If you are using public transport then buses to Foxdale are not that frequent - use iombusandrail.info - however you best bet might be an early 8.40bus to peel - get off at St Johns - look at Tynwald for a few minutes then get on the number 4 bus from Tynwald (bus stop just on Peel side of Tynwald grren that takes you to Foxdale mines rd in about 10mins - spend an hour and a half taking in the sights of picturesque Foxdale (locals can do this in 5min - it is not the prettyest part) - walk upto St Pauls and find the grave then get the 1104 bus back to Peel.
You can buy 1 day 3 day etc rover tickets on for the buses from the info centre at the Sea Terminal - your best bet