Hi I would say its the wrong time of year you should of done most othe pruning in Autum, as the sap is rising I would wait until the summer prune.
Are you able to bend the branche down to slow the sap as it might encourage other shhoots to break you need to get a good book and read up as on here it would be complicated on what to do.
Considering how old they are waiting until later in the year would have no depremental effect
Hope this helps a bit
Spruce